SLI is a 3dfx technology from the voodoo 2 days and video cards werent even relevant untill the voodoo3 days because you needed a seperate 2d display adapter.
Video games havent been relevant since games stopped supporting software rendering and requiring video cards.
3dfx didnt die untill they tried to bring SLI back after voodoo3 then nvidia bought em out.
nvidia is using a flop technology.
Software renderers can do more advanced graphics than graphics cards because they arent limited by a certain version of some api like direct x 11.
SLI as was used by 3dfx was a completely different technology than what Nvidia currently uses, back in the day they used Scan Line Interleave (SLI) which meant each video processor would render an alternate scan line and then these would be merged to render an image.
While it's true that Nvidia bought all of 3dfx' assets including intellectual property, their multi GPU technology just uses the old SLI moniker (which stands for Scalable Link Interface in this case) but it's a completely different technology, using alternate frame rendering for most games and applications (FYI, AMD's Crossfire uses a very similar algorithm)
As for whether software rendering is better than 3D acceleration, this debate was settled back in the mid nineties, and to be honest, I don't know if you're just joking there...
Some rendering techniques like ray tracing are in fact very similar to a good old fashioned software rendering mode, but these are too slow to be used in real time for games, and are used mostly for CGI, but that'll probably in the future as more computing power becomes available to developers, but for know, hardware 3D acceleration offers both the most economic and faster way of rendering games, and will remain so for the foreseeable future.
I don't know what you mean by video games not being relevant, as an industry it has surpassed all other entertainment industries in terms of revenue, and in record time no less, dunno what your point is.
Back to the topic, Mike, can you download 3DMark 11 and post your current score?