I had this issue a long time ago and I already posted it in here and everyone told me its normal for a game such us assasins creed2 and r.e5. but i cant help getting annoyed with the anti aliasing/shadow issue. Ive posted a few videos using fraps and converted them in mp4. quality is still good and you can easily notice the bad anti aliasing in the shadows. ive only got the problem when there are shadows in the game.. please download and view the videos..
http://www.megaupload.com/?d=0VBKKK1C
here's my system setup
Proc: Phenom X3 720 2.8ghz B.E
Mobo: Asus M4A89GTD Pro USB 3.0
Ram: DDR3 G.Skill Jigsaw 1600 cl7-8-7 24
V.Card: Sapphire HD4770 512mb Gddr5
No overclocks have been done yet.