My 2009 iMac 21.5" plays everything I throw at it...well games I'm interested in.
Core2duo 3.06ghz, 6gb 1066mhz ram and a Radeon 4670.
Star craft 2 on max, counterstrike at max, portal, c&c3..erm....company of heroes not so good at medium.
So I dare say a brand new iMac with corei3 or i5...