I got my mini NES mostly as a collectible and novelty item. I am still going to play a few games there, I was thinking of playing Metroid and Kid Icarus but as has been mentioned, these are games already available from different places. Several of the build in games I also own on my original NES too so the buy was pretty much for collecting reasons.
Well and I also got the Mini Famicom that is own its way... I figured, if I already own an original NES and an original Famicom - Why not get the mini version of the latter as well
..I just hope they don't decide to release mini Game boys or mini Virtual Boy or things will escalate very quickly as I would want a mini version of everything I already own