Ok, so I only completed this game on the Wii with my daughter.
In the past, I had a chance to occasionally play it on PCE (fellow enthusiasts) and I always dismissed it (I wanted to try out other games). This was not a fair way to judge Bonk 3... but for 15 years I simply thought it was "OK"... Again, based on my lack of enthusiasm for it relative to other games (like Soldier Blade), and not for any particular problem with Bonk 3 itself.
I can't speak of the 1-player experience (I've played sporadically over the years), but it was fun as a 2-player coop, even though it suffered from the typical "oops, the leader has to backup/backtrack in order for partner to advance. Personally, I don't think this is a flaw, it simply is the nature of 2-player games of this sort.
Now, a more annoying issue is when one/both players must be BIG/small to pass a point: you have to backtrack/maneuver for candy to respawn... It's not horrible, but it can be slightly annoying if one of the players has "low SKILLZ" (my daughter improved).
Bonk 3 HuCARD wasn't a particularly challenging game (none of the PC Genjin's are), but overall it was WAY more enjoyable than I thought it was going to be.
I still haven't given this game a fair 1-player outing, so I will reserve judgement on it.
For the record, I do *not* consider Bonk's Revenge to have supreme superiority over Bonk 1 (when Bonk 2 was released, I *did* feel it was *vastly* superior to Bonk 1, but my opinion of Bonk 1 have changed over the years and now I *love* it more than I ever thought I would).
So, with that in mind, I am willing to give Bonk 3 a real chance to win my heart.
As for Bonk 3 CD—I never really played it (briefly with friends), so I can't judge it.