I started with AD&D 1e and red box D&D, progressed to 2e (which I thought was a good game, despite the hate it seems to get), progressed to 3.x for a while, and now to 4e. We always had a blast with 1e/2e, but 3e felt hollow and unsatisfying for me and my players. It shifted so far in tone from the games I grew up with and loved (namely that it was focused on mechanical character building and micromanaging resources) that I just couldn't find it a satisfying gaming experience. For me and my players, 4e has brought D&D back to its roots (especially reminescent of the 1e/red box days), and we're having a blast with it.
I tried Pathfinder during the beta period and into the final publication version, in a campaign I played in from levels 3-11 (I had a dwarven cleric). While some things were cleaned up in Pathfinder from 3.x (CMB/CMD, somewhat consolidated skills list, slightly better balanced non-caster classes, spell revisions), these were minor improvements, and the basic problems I had with 3.x were still present in spades in Pathfinder. Casters still rule, magic items ARE the character (Xmas tree syndrome), GM prep time is horrendous, summoning is a pain, the magic/spells arms race between DM and players is still there, the math is still completely wonky, and the highly touted extra options in the system don't really add anything IMO (just more complication). Finally, the high wahoo factor (yes, much higher than 4e IMO), increase in overall PC power, and art for Pathfinder were major turnoffs for me.
If 3e was the bees knees to you, then you'll likely LOVE Pathfinder. Pathfinder isn't a bad game at all- its just not to my tastes. I will say I still buy the PF APs and some modules- they are generally very well done, and have cool ideas to steal for my 4e games. I tried for years to run the kind of games I did in 1e/2e in 3e, and found it was very difficult to do, due mostly to the changes in assumptions of the game 3e made. From what I've seen of Pathfinder, it has exactly the same characterstics, strengths, and limitations as 3e. 4e has brought back the glory days of my 1e/2e games with its different design parameters and more "old school" philosophy, and I'd never go back to 3e/Pathfinder at this point. The few things I didn't care for in 4e we easily houseruled (long-term injuries, more flexible ritual casting rules, and "more magical" magic items), and for my gaming style, 4e is scratching the itch perfectly.