Mediocrity in HL2 and Crysis? Uh huh. You can have the others but those are were not mediocre thank you very much.
Each to their own. That's my opinion of the games.
Strip away the graphics of Crysis and you're left with a bland, fairly lifeless game that added nothing to the genre. The first half of the game before reaching the alien ship was passable, but no Far Cry. The second half was just boring. It felt like the developers were just focussed on achieving the best visual impact they could come up with, with no regard whatsoever to how the game played. I think they just wanted to produce an advert for their engine.
HL2's 'averageness' is a bit more subtle to describe.
I think it had a lot to live up to because Half Life 1 was such an incredible game. I was really excited about the sequel, and the E3 trailer that came out had me convinced it was going to be the next coming. However, it just didn't feel all that fun when I eventually got to play it.
The weapons seemed to lack any feeling of impact - the combine soldiers just seemed to stand there like cardboard cut-outs whilst you fired at them - then they would just drop to the floor. The gunplay can make or break a shooter and, for me, HL2 just felt very wooden and didn't succeed on that level.
Then there was the whole 'scripted experience' thing. I think the scripting and set-pieces were what made the first game so ground-breaking and so Valve obviously wanted to continue in the same vein; but in trying to take it to the next level it was almost like they tried to pull off too much.
They clearly had some great ideas but it just felt like they tried to cram in one set piece after another, then polished it all up so much that the experience lacked that raw, gritty gameplay factor that has made other games play so much better.
I think at the end of the day HL2 was just a victim of over-engineering and although I certainly wouldn't class it as a bad game, I was left with no particular desire to play through it again like I have done with other, better games.