I've given up on D&D and went to Pathfinder. In many ways, they are cleaner rules IMO. Many call it D&D 3.75.
D&D 3.5 was probably my favorite of the true D&D versions. Cleaned up rules from 3.0 and less confusing combat and skill system (due to the d20 system from 3.0).
D&D 4.0 was good for dungeon crawls and games involving lots of combat. You could still roleplay with it, but the mechanics within the system weren't there. The GM could make up house rules but that takes time and effort which many GMs don't have. I did like how thematic each class could be within a combat and spellcasters weren't 1-shot wonders and fighter A wasn't the same as fighter B.
D&D 5.0 has come out. I know some have begun to play it and I've made a character in it. It kept some of the 4.0 ideas, added RP mechanics back in, but I can't speak for gameplay.
Hope that helps.