the game scales waaay up on the high end and had a lot of features built in that basically didn't run at all at playable framerates on 2007 hardware. HBAO especially is computationally expensive.
Crysis 1 didnt have HBAO, it had very unoptimized SSAO, because they pioneered this technique.
For example in Crysis 2 they increased SSAO quality and still improved its performance 10 times.