There were no retro-clones, when I started playing D&D again as an adult. I wanted to start playing a fantasy role playing game, and had a setting in mind for it, but I wasn't sure, which version of the rules to go with. That it would have to be Dungeons and Dragons, of that there was no doubt. Reason being the multitude of monsters, treasures, magical items and spells. I knew that from previous experience. Gygax rolled over the hobby like an avalanche, and then succumbed to his own flaws and excesses. Left in his wake were other systems for playing fantasy adventures that had to be smaller and carve out niches for themselves. It was a meager existence. Consider the golden age of computer role playing games such as Baldur's Gate, Icewind Dale, and Planescape Torment, who had license from the D&D franchise to use D&D intellectual property, the Arcanum (of Steamworks and Magicka Obscura), that did not. Essentially it was the fantasy version of the Fallout game dressed as Steampunk. Except that they couldn't introduce a lowly Orc or a Goblin, nor a Magick Missile, nor Fireball spell. The deficit was painful, the dungeons bare and stocked with predictable Wolves. A few game mechanics foreshadowing Farmville making the gameplay addictive, and they had a few good ideas and story twists, a few truly terrifying and tragic concepts, as well as one concept that did not work too well, that foreshadowed the bottom levels of the Legend of Grimrock, but that game was decidedly a wanting experience.
So, I was going to stick with D&D for its infrastructure. The question was, which version? D&D includes a number of distinct product lines, which play differently. TSR was a monopoly and in its quest to be the Standard Oil of fantasy role playing games, it tried to be all things to all people and it ventured outside the scope of fantasy genre to create versions of basic D&D for the other genres with various degrees of success. Of these, the most notable one was the Gamma World. It was a unique game with unique game mechanics and a unique setting, and all of the elements worked I harmony to create a whole that was greater than its parts. First edition was a relatively dry sci-fi adventure game. The colorful second edition was more of a fantasy war-game with an established world, to the first edition's ruined universe waiting to be explored. I preferred the survivalist-oriented tactics based Aftermath! at the time. As with all things TSR, the subsequent editions of the Gamma World, up to version 5, went in the direction of ridiculous, where players can give themselves desired superpowers by means of cyber potions and injections. Second noteworthy game from TSR was the Wild West themed Boot Hill. The rules were ground-breaking, because at Boot Hill came out at the time of the White Box D&D Edition, and its rules were advanced and elegant when compared with White Box set. Problem was, rules dealt largely with gunplay and they never really developed it as a role-playing game, maybe there was weak public interest. Since then, there are two excellent indie games dealing with the same topic - Dust Devils and Dogs in the Vineyard. Top Secret was the D&D set in the world of espionage, and it was the worst game of the bunch. It has two useful game mechanics one can adopt to any game - random site table for encounters and fields of background knowledge. Basically, a list of wide fields of knowledge, that a Player Character is aware of, and has a good chance to know the background information in the story pertaining to those fields of knowledge. Say a PC knows Architecture, s/he can tell something about the temple the player characters are about to enter. Star Frontiers was the TSR's poor cousin to GDW's Traveler, and that's about it.
With regards to the fantasy role playing games that competed with the D&D, there were many, Rune Quest, Tunnels and Trolls, Chivalry and Sorcery, Man, Myth and Magic. This was in the days before the internet, where the people behind the game were mysterious entities you entice to write back with an SASE (Self Addressed Stamped Envelope). I could never get the Chivalry and Sorcery, I may not have had money at the time. The game was complex, and from what I read about it, dealt with the historical realities of the Middle Ages and only introduced dungeon crawl after it lost to D&D in popularity. You had to travel around the countryside, joust, etc. I was impressed with its magic, it not like D&D, spells took rituals and long time to complete, one, for instance, turned a pool of water into as crystal ball under the moonlight, and required an entire afternoon. Not the Fireballs and Magic Missiles. Rune Quest offered an extremely elegant skill system I had to adapt for my version of Dungeons and Dragons. Tunnels and Trolls did not offer anything, except a magnificent list of exotic and unusual weapons. Six versions of a spear, anyone? Well, yes, that would be me! In an effort to make Midlands attractive to all thinking players, I had to make it as challenging to Fighters as it is to Magic Users and Thieves, which means that the Fighter's choice of weapon (skill) and armor had a consequence on their fighting style, or more correctly, if a player behind the fighter character has a brain and knows something of medieval weaponry, s/he can decide on a fighting equipment to match their tactics in battle, and gain a significant advantage over a player who just rolls to hit. That called for the use of the Gygax's infamous Weapon vs Armor table, and I also added a few other dynamics to surprise, movement, and initiative, to make the melee worthy of a thinking player, where a critical hit can take any opponent out of the fight (but not necessarily kill them!). Of course, Monsters get the same rules and I have had player characters killed with a well placed blow. Spear, being primarily a hunting weapon, a certain type of spear will give a bonus in a certain situation.
Having decided to zero in on the D&D rules for its great variety of spells, monsters, magical items, and treasure, I needed to decide whether to use the White Box, Basic - Expert, or Advanced D&D. White Box set was too vague. Information was raw and better elaborated on in the AD&D, so I cast it aside. The Holmes Basic Set was a stripped down version of D&D for beginners, but it had two golden paragraphs, one explaining encumbrance, and the other general advice to starting DM's. The Basic - Expert D&D line initiated by Tom Moldway and culminating in the Rules Cyclopedia is a different game bearing the same name. While starting out with the simplified rules and fewer spells and monsters, it took the players in a different direction, that of high level campaigning, waging wars and running kingdoms, and achieving near God-hood. Moldway is a genius at explaining adventure design to novices and his section on adventure design in his basic rulebook is the best written and is a classic. For reasons of complexity, he could not do the same for Wilderness design, and Gygax himself simplified the Wilderness adventure design down to the concept of a hex crawl. I started with the Moldway Red Box, and it took me almost two years to figure out how to use the percentile dice correctly, but I moved on the Advanced D&D, FIRST Edition, on the strength of Gygax's writing and detailed game mechanics of his Dungeon Master's Guide. After Gygax left the TSR, the subsequent editions scrapped his writing on dungeon and adventure design. There was an editorial desicionmade at TSR, and subsequently reinforced at WOTC to reduce the DM from the Gamerunner to the Referee. For reasons of marketing, most products deal with customizing and empowering player characters, appealing to Munchkins. DM's are encouraged to use the pre-written adventures. The target audience has dropped in age from a grad student to an early adolescent. The scope of dungeon adventure design has also shifted from the dark labyrinths of the DM's twisted mind to the pencil and paper version of the Diablo videogame. There is a reason why the concept of the dungeon adventure trook off and spread like wild-fire. A dungeon map also serves as a flowchart to an adventure - a series of encounters connected by proximity lines (corridors) in a schematic.
The first edition of AD&D was perfect for me. I expanded I into Post-Gygax 1.5 and as far as 2.5 Core Books to see if there was any new writing on adventure design, but there wasn't, only simplification and repackaging of the 1st Edition. I have the entire catalog of the AD&D 2nd Edition rules and supplements, and they are a disappointment. In the Second edition, AD&F tried to be all things to all people, they just dragged the whole of 20th Century life into the game and dressed it up in the fancy robes of Renaissance. I am not a fan or defender of Gary Gygax, but his Dungeon Master's Guide is his best writing and it is superior to the later versions of it. Way back IN 2003, I started re-reading these books as an adult, and having read halfway through the Gygax introduction to the fist edition Players Handbook, I was taken aback and impressed by the quality of his writing - his sense of history and philosophy behind his rules.