I don't know how this thread turned into Mario 2... but I like it!
I always hated Mario 2 when I was younger. I also really enjoyed the lost levels when it first came out.
Then a few years ago I picked up a Famicom Disk System for the first time, with Doki Doki Panic. When playing the game without Mario in it, it helped me realize that it really was just a very good game. I had blindly hated the game for years, not because it was bad, but rather because it didn't feel "Mario" enough.
Now I am actually a bit of a Mario 2 addict. I played through and beat Doki Doki, Mario USA, Mario 2 NES, and Super Mario Advance (which is the definitive version). Other than Super Mario World and Mario 64, Mario 2 is my favorite in the series.
...Mario 2 Japanese version on the other hand? Yuck... just makes me mad to play it now.