Which stealth games can you recommend on XBOX 360?

I loved the Hitman series, Manhunt 1 (Manhunt 2 wasn't as good) and the Splinter Cell series on PS2. I love the whole sneaking around thing as opposed to just shooting the crap out of everything. Have played Splinter Cell Conviction on XBOX but it wasn't as good as the previous games. I believe a Hitman 5 is/due out? What other games of this genre are good? Is it true that MGS isn't very realistic?