Well I have both EPS08 and Fifa 08. Only played Fifa last night and it seems good.
With PES you get a LOT of troubles online, loads of lag (so much lag that the OCuK Tourny was cancelled and replaced with a Fifa one). So this current generation fifa wins, though I still find PES the better to play.
It depends though really, both are similar to the previous generation of games, so which ever one you prefered, you go for that one.
Assassains Creed isn't indepth and can be very good. It is a bit repetative, but I never found that a problem, it was just really good fun in my eyes.
Kane and Lynch, probably give that a miss then,
Mass Effect is very indepth so give that a miss too.
if you like forza and want more of a "Arcade" racer, than PGR4 would be a winner with you.
Saints row you can pick up uber cheap too, which in my eyes is well worth it.
I'd go with: PGR4, Saints Row, and Assassins Creed (check out the videos though and reviews before you buy this.) as it might not be your thing.
I'm sure someone else will be in here giving their opinion too!