So what you're saying is one game... you've never played has less story than another game.
You've never played.
The plots of Half Life and Doom are almost identical; add in the Half Life style 'everything's not gone to hell yet' opening sequence in Doom III and the game IS nigh on identical.
Except Doom III has all the PDAs and the like, and some kind (but not much) explanation. To be honest, Doom III has a much more fleshed out plot than Half Life.
In Half Life, and to an extent Half Life 2, you're just bumbling along from event to event, with very little (if any) exposition. In HL1, this is done by the G-Man. In HL2...
Time, Dr Freeman?
That is all, to an extent, true, but it's based on opinion.
It's an immersion thing, something that most games do very badly. Look at Doom III; you keep going to 3rd person all the time, which is just idiotic.
It's also something that almost all games have copied. Halo has it, don't forget.
It takes about 5-10 minutes at most, and for quite a lot of that you don't actually have to be at your computer. What kind of attention span have you got?
Don't play Half Life 2 without playing Half Life 1. You'll miss a lot of the point of the events, and all of the references to the previous game.
Furthermore, quite a lot of the game is designed behind the idea that you've played HL1; the enemies, for example.
And you gave up on Deus Ex because you didn't like the graphics? Christ. I don't like the Unreal engine either, but that's fairly extreme.
No-One Lives Forever. A spoof '60s spy game by Monolith, the makers of (amongst other things), Shogo: MAD.