If I could only have one system, it would be the SNES, so to me its the best ever. The NES may have been where alot of the classics started, but the SNES is where they reached their peak. Super Metroid, Super Mario All Stars, Link To The Past, Final Fantasy 3, ect... Then you have great original games too like Mario Kart and Chrono Trigger.
I like alot of the older systems like the Neo-Geo, Saturn, PC Engine, and Dreamcast. But the SNES was hands down Nintendo's best system, and had the best ratio of good games and variety out of every console.