The first Half-Life is great, but I always felt HL2 is much worse than HL1 for multiple reasons. HL2 simply don't deserve all the praise it got as far as I'm concerned <_<
- Running around in some top secret lab facility was fun, running around in some half-ruined city and sewer is not. I was very amused when I saw the periodic table for the first time in HL1, for example, and how some parts slightly reminded me of the high-security areas of the OKG nuclear power plant where I have worked.
- It also annoyed me how everyone react to the almighty super hero Gordon Freeman. It was better when he was a nobody.
- The physics-based puzzles just bore me. They aren't hard to figure out or anything, it just takes time to put enough stuff where it's supposed to be and then you can go and continue to kill enemies. For me they just felt like an unnecessary obstacle to make the game seem longer than it actually is. Same with the driving sections.
- The thing I miss the most from HL1 is how one would see different enemies fight eachother. The evil aliens vs the bad military guys. If you just stayed out of it, they would keep fighting eachother. In HL2 is always just us and them. There's no third part, and that's what made HL1 special to me compared to the previous shooters I had played at that time. Well, the antlions first just fight "us" and then switch sides thanks to a new weapon and are then used to fight "them".
- Oh, and I'm also annoyed that Half-Life 2 is the PC game that introduced the need to activate the game online to be able to play it, even though it's a single player game. Although that doesn't really have to do anything with the actual game, but I list it here anyway.
Errr, a lot of complaints, I guess. But yeah, while the actual gameplay didn't change that much between the games (the action is still top-notch but I think http://en.wikipedia.org/wiki/F.E.A.R. have even better action and thus is a better FPS), the whole setting just fell flat for me. This while the only flaw of HL1 is pretty much the last Xen area. I look forward to the http://blackmesasource.com/, seems like a very good remake of HL1 for the HL2 engine.
I think that the Portal series is easily the best thing Valve has created though, both the first and second Portal are awesome games and I had lots of fun playing thru the Portal 2 co-op levels too. Left 4 Dead is quite fun too to play with friends. Also have Left 4 Dead 2 but I barely played that one, still lots of unplayed campaigns there, but good so far.
The rest of their games, CS: Source, TF2 and so on, are games I don't really care about so I can't comment on those