Sorry, but you're totally wrong.
Play(load a level under medium settings), and PLAY are two different things

There is NO MAC (much less the mGPU blessed iMac) that can max Crysis (@ native res) at livable frame rates(>30)...especially not at 2560x1440.
That said, I get the whole "talking about Crysis as THE end all graphics benchmark is cliche"...but it IS STILL A VERY relevant benchmark, even by today's standards. BTW: What do you think is current "news in the graphical world"? Metro 2033, Crysis(1, WH, 2), AVP...those are CURRENT BM heavy hitters
Crysis 2 is much more optimized than the original, that and it's setting facilitates easier processing and scalability(dense organic Jungle vs. city).
The iMac is great for most Blizzard and Valve titles... I use my mac for everyday *user experience oriented* computing (email, Garage Band, photos, iTunes...etc) and I love it....Gaming PC for all else.