From my experience, the only game I've ever gone from liking to strongly disliking has been 3.x.
When it first came out, I hopped on the 3e bandwagon. I had played and DMed a lot of 2e, and still enjoyed it, but all the extra little fiddly bits 3e added looked cool and interesting, plus it streamlined and made many things more intuitive (saves and BAB for example). At first, I really enjoyed 3e, and we played a ton of it. But as we continued to play it over the next year or two, a lot of things began to bug me, especially from a DM point of view. The prep work was monumental compared to earlier editions for no noticable increase in payoff or performance, the system mastery component of the new rules really bugged me and I felt detracted from the immersiveness of the gaming experience of my players, the math and power progression was seriously flawed and wonky as hell, the casters dominated non-casters, magic items were far too important, and the core assumptions of the ruleset didn't match what I wanted from D&D. In short, it didn't feel or play like the D&D I grew up with at all. My players were still mostly enjoying it at that time, so I bit the bullet and continued to play and DM 3.x until about 2005, when my entire gaming group suffered serious burnout on 3.x and were actively disliking it. We never really got on the supplement treadmill, and played with mostly the core books, so the power creep and wonkiness didn't really creep in for us. 3.x was just a woefully inadequate tool for running the kinds of games I wanted to run, and it wasn't worth trying to pound a square peg into a round hole to try and force it to perform up to my expectations.
I've tried playing in 3.x games and Pathfinder since 2005, and I find my distaste for the system continues to grow. There are numerous reasons why (which I stated above)- but the most annoying thing is that the base rules system and assumptions it has takes attention away from actually playing the game and roleplaying, and focuses on optomization, build, and system mastery. This isn't just for my group, but other people I've gamed with as well. I've seen many people who I have gamed with before and know are great roleplayers devolve into munchkin twinkery when 3.x (or its derivatives such as D20 Modern) comes into play. Switch to another system, and the problem goes away. As for why this occurs, I have no idea, but its a strong recurring pattern I've noticed over the years (although obviously not everybody who plays 3.x has this problem).
Its not so much that I hate 3.x, just that I find the system fatally flawed, and it does not fit my playstyle and preferences. It took me a while and some experience with playing the game to really realize this- even though I liked 3.x in the beginning. I have found other RPG systems I really enjoy and which do fit my likes much better (such as BRP CoC, Savage Worlds, WHFRP2 and WHFRP3, Dark Heresy/Rogue Trader, nWoD, and D&D 4e).