It's so hard to tell but since your question about the ERA, I'll consider games such as SSBB and New Super Mario Bros as 3D era rather than 2d.
I grew up playing 2D games and to be honest, I'm not sure what I prefer. Sure, 2D platformers had more action than 3D platformers (Sonic, DKC) but I really liked Banjo-Kazooie and Super Mario 64 so I can't tell which I prefer. I would say 2D only because there were more games than 3D in the platforming genre.
Some genres are much better with 3D: RPG, FPS, racing games, sports games, etc.
I can't really say I prefer either era. The only thing I can think of is I believe that with games costing more to produce nowadays, there are less quality titles coming that there was.
How many cups of darkness have I drank over the years? Even I don't know...
