I remember being interested in Bonk from a snippet of gameplay in a TG-16 commercial, but I didn't play the game until about two years ago. The graphics and general theme appeal to me, but it's not a game that I play very often.
In comparison to Sonic/ Mario, I dunno.
When Sonic came out, I was a bit disappointed that it was so popular. I had a Genesis, so it was cool that the system was really taking off. But it wasn't really the kind of game that I liked. The colors were nice, and the scrolling was neat, but I didn't really care about scrolling at the time. I was mostly into RPGs, or strategy games- we generally didn't buy a game unless it had a save feature (with the exception of Strider- it was kind of a big deal at the time). I do like the Sonic games now (especially Sonic 2), but more as an example of programming prowess and creativity.
I think that it's not a stretch to say that most every Mario game is enjoyable without regard to context. Super Mario World was the kind of deep, exploratory game that I had wanted Sonic to be.
Finally playing Bonk was cool, because I remember seeing the art style and reading about the game play mechanics. But they're not the type of games (aside from maybe the giant Bonk sprite) that show off what the console can do, nor do they provide the kind of deep gameplay of Mario.
Then again, I was 30 when I first played Bonk- maybe I would feel differently if I had secured a turbo in 1990.