Lost Levels was quite good, (definatelly the hardest Mario game out there) but I still like SMB2/USA. It's still a pretty fun game, I felt. Still remains one of my favorite childhood games. (In fact it was the first game I ever beaten.) And the "pick up & throw" mechanic (wich I liked) did make it's way in some later Mario games, (Like Donkey Kong '94 for Gameboy & New SMB Wii) so the game doesn't feel to "out there," and not like a Mario game to me.
I also liked how the Bob-ombs, Shy Guys, Ninjis, & a few other enemies from DDP did carry over into the Mario series. So I feel some good things did came out of Super Mario 2/USA.