Mass Effect isn't a turd, imo. The optional sidequests are ridiculously mindnumbing and I'd only suggest doing maybe 1 or 2 at a time but overall ME is a pretty damn good game.
Nate of Persia however....ugh. Is there a demo somewhere? If there is, try that 'cause that's all you'll ever need. If not, no big loss. The best thing about PoP was the trailer with Sigur Ros.