Mario games: Unquestionably love. Every reason I could say everyone has heard.
DKC: That's a little more complicated for me. I was in love with the first SNES one when it came out. Unlike most people, the DKC2 didn't thrill me too much. I enjoyed it, but I felt...off about it. To this day I can't quite explain it. I never even bothered with DKC3 because by the point I lost interest in the series. I didn't really replay any of them for years afterward, and kind of forgot about the series.
Then DKC Returns got me back into it. I didn't think it was a GREAT game, but a good return to form. These days, I like the original DKC, and am starting to appreciate DKC2. The third one I still have yet to play. I hear, oddly enough, that the GBA version is better than the SNES version.
