Not to tramp over anyone's parade but...
I've actually seen quite a few people think about Crash Team Racing (The Crash Bandicoot Go-Karting Series) And was thinking that perhaps some of those maps are worth a port. I've considered porting one, but I've got enough on my plate and want to finish that up first. Some of my friends, as well as in other netgames, thought it would be fun to add some of those maps in. Like Clockwork Wumpa, Cortex Castle, Hot Air Speedway, Nitrous Oxide, some of them actually have interesting styles to them.
Additionally, it wouldn't be hard to remake with SRB2's level design actually. It uses colormaps just like SRB2 does, as well as the topography! All it needs is custom textures, and it should be all set, actually. I feel like doing some textures for it maybe, I just need to get that game back.. somehow. As well as texture rips.
But anyway, no more rambling.
My tl;dr statement is, there are also lots of CTR and CNK fans, and perhaps trying out some of those levels are worth a shot :P
EDIT:
I think we should focus on more variation in the track themes. For example, we don't yet have a Bows-, uh, Eggman's Castle stage. And we definitely should focus less on ports since, as you've said already, we already have enough of them.
OH yeah, I actually remember someone trying to make a Bowser's Castle. It was a lot of fun.. I really wished they would continue it.
Secondly, someone DID try to make an Eggman Castle back about a year or so ago. I think it was by Fawfulfan. You could talk to him about it if you want. The Bow- I mean, Eggman's Castle he made was not that bad, but it kind of lacked playability. It was very hard to maneuver around some parts. It didn't have a lot of "Eggman" in it either.
And before I forget.. I have yet to see an Egg Rock Zone style map for SRB2Kart. That would actually be rather fitting. Driving on ceilings, anyone? ^^