Back in 2007 Crysis was the most demanding game of it's time and remained so through 2010 or so. Graphic cards could really catch up to the performance required to max out that game with ultra settings @ 1920x1200 (and 1920x1080) and still get good frame rates (51+ FPS) until around mid-2011 with a single card.
I think the 1st card ever to get pretty good performance was the Radeon HD 5970 which has two GPUs in on the card back in 2009.