Neonchameleon
Legend
Gygax's game had nothing to do with "adventure paths". Look at the style of play described in his DMG: the GM is running the game basically every day (every real world day = 1 game world day), and those players who can turn up and choose a PC to play and do stuff.
Tomb of Horrors was adapted from Gygax's campaign. (He designed it to defeat one of his players - I think @Neonchameleon knows the story.)
All correct

(My source for the story behind ToH is Mike Mornard/Old Geezer on RPG.net).
As for fighters vs spellcasters, Gygax spent a lot of time balancing fighters with casters for oD&D. He failed because the main fighter player was Rob Kunz - who amongst other things had a superb working memory and a lot of skill as a player. But most of the fighter balancing mechanisms were subtle and included rigging the loot table hard towards fighters by making it mostly swords (which clerics couldn't use), making swords do extra damage against large creatures, putting in a de facto level cap round 10th level, and giving fighters the best saves in the game. There was also a lot in the game to subtly weaken wizards - like save or suck and save or die spells being much easier to save against, spells known coming under the heading of loot that was assigned by the DM, a very limited number of spells per day, spellcasting disruption, powerful spells having drawbacks, and much more.
Every single one of these boosts to the fighter was either massively reduced or eliminated by 3.0. And every single one of the wizard restrictions was either removed or eliminated by 3.0. And they didn't go far enough - Gygax posted on these very boards that the reason for the seemingly overpowered fighter variants in Unearthed Arcana (like the Cavalier) was for balance, giving the non-casters a much needed boost.
But what really demonstrates the fighter/wizard balance problem is that we're talking about it. It should be an apples/oranges comparison. For balance purposes, the fighter should be compared to the spellcaster who can heal (therefore bringing far more endurance to the party than the fighter ever will) and bring down blessings for the rest of the party - but doesn't have many strong overt magical effects. The wizard should be compared to the lightly armoured utility guy who has a tendency to go squish in combat and hides in shadows pretty well. If the wizard is being compared to the fighter in terms of combat potential something somewhere has gone deeply wrong.