The CoD series (same old, same old)
The Halo series (over-hyped, but not a bad game per-say),
WoW (more addictive than fun),
Fallout 3 (average gameplay with a rubbish ending),
Bioshock (I played the game through using only the wrench, and no RPG elements).
I don't understand why a lot of people don't enjoy the Half-Life series; I assume most here are people under the age of 20 that never got to play the original Half-Life in it's prime time (including the expansions), and that most here probably never played some of the fantastic mods created for the Half-Life engine (Natural Selection specifically), but in no way is the Half-Life series bad.
I'm currently replaying through Half-life 2 to Episode Two and so far, the weakest point was probably Episode One. I'm almost finished with Episode Two, but even though I've played through the games a good 5+ times now, I still enjoy them as much as I used to, especially Episode Two.
As someone said, you have to immerse yourself in the Half-Life story to realise it's potential for greatness. 99% of people who play Half-Life 2 just think "lal aliens kill and gorden freemun attack bak lolz" when really there is a hell of a lot more to it than just that. If you seek out and try to understand the story, you'll realise that it's a story that could continue on indefinitely and could go anyway.
I think the biggest problem, though, is that if you haven't grown up with certain Half-Life elements from the original game, most of the sequel won't mean that much to you. EG: Barney offering you a beer, Dr. Magnusson and the microwave casserole, the Vortigaunts now being allies and, of course, the G-Man.
You can't even play through HL2 for the first time these days, because it's 4 years old. Half-Life created first-person scripted events (in which you can still move around), the gravity gun, real-time manipulative physics and some very fantastic and unique weaponry. And even if in this day and age the gameplay doesn't quite match... err... Crysis? I can't really think of a game that's more fun than Half-Life... ahem, even if it doesn't match up, it still should be appluaded for being fantastic.
Ranting aside, I think if you just throw yourself into the Half-Life series and say "I'm gonna see what everyone is talking about... blah blah blah, shoot that guy, I don't care about you Alyx so shut up... kill that headcrab and attack that zombie" then, of course, you aren't going to enjoy it. But that's the same as any game out there, and I've found that if you try a game with a negative attitude then you're only going to get negativity out of it. Hype can be bad for a game, and if you try a game thinking it's the best thing in the world ever even though it's 4 years old, then of course you're going to be a little disappointed.
Heh, there's a reason both the Half-Life games have 96/100 on Metacritic.