If you like realism, why not go for the Tom Clancy series? Rainbow Six 1-3, Ghost Recon, and Sum Of All Fears are excellent realistic shooters. Although they pretty much threw realism out the window with more arcade-style games like GR: Advanced Warfighter and RS: Vegas.

And, of course, my favorite... Operation Flashpoint. ArmA and ArmA 2 as well, if you liked OpF.