My favorite part of most games is the beginning couple of hours.
GTA San Andreas- Only really fun in the first city, when you're taking over turf. Once the game opens up, it dives into ludicrous territory in a vain attempt to remain interesting.
Morrowind- Explored the hell out of that island, maxed everything out(you can pay to level!), then realized all the quests were now piss easy, so I didn't bother with the actual story. Probably played longer than most people who bothered to beat it. Wonder whether Bethesda would consider this a rousing success or utter failure.
Call of Cthulhu: Dark Corners of the Earth- I'm ashamed to admit this one, since by subject matter I should like this better than Half-Life. I like shooters, and I like stealth, but I don't like when a game forces me to flee. The triggering of the fight or flight instinct is what makes games fun. Why take that away, and why limit it to flight if you do?
Scarface- Fuck this game for its end level. No saves, and infinitely respawning maricones. They might as well have put in a time limit too.I hated Modern Warfare's end level, but I finished it because it was a good game.
Halo- It's not as fun as you think shooting Carebears. The second level was getting better, until I had to deal with the fuckin Warthog. I quit.
FEAR- Never understood all the hype. Played about four levels in, and didn't get in any fights that were half as fun as fighting the soldiers in Half-Life. Only part I really liked was the guns. Then STALKER came out.
Max Payne- Again, overhyped. The game forces you into a very specific strategy. You can't really survive without bullet time, which I think is cheap. This is the only shooter my girlfriend likes, so I tried it. Then FarCry came out. I had her try that game, heh.