It's my humble opinion that Duke Nukem Forever is a lackluster video game that piggybacked its way onto front page news solely because of its name. The game is boring, unoriginal and will likely only appeal to young teenagers or diehard Duke fans that just can't let go -- and that's hard to write considering we've been following the project since the late 90s.
On the bright side, if you're actually interested in playing DNF, at low resolutions the game can be played using the highest visuals settings with budget graphics cards, such as the GeForce GT 430 and Radeon HD 5670. Neither are gaming cards but are able to score 60fps at 1440x900.
Along with having low GPU requirements, you should be able to experience playable performance with a modest dual-core CPU. We imagine you could pair a $60 GPU with a $60 CPU and still play DNF as it was meant to be played. In fact, you could scrape by with Sandy Bridge's integrated graphics core if you're willing to lower some of its visual quality settings.
The last flagship GPU to provide a similar bandwidth as the GT 430 (28.8GB/s) was 2004's GeForce PCX 5950 (30.4GB/s). In other words, for DNF to have been the "Crysis" of its time, it should've been released about seven years ago.
Graphics aren't everything and countless visually-stunted games have become cult classics, but we don't expect that to happen with Duke and that's a shame after so long.