Confession: I'm pretty burned out on MetroidVania. I've played all of the 2D Metroids and beaten all of them except for 1 and 2 (they didn't age well). I've begun playing the Prime series. I've beaten Symphony of the Night and 2 of the 3 GBA Castlevanias. I've played and beat Herocore (Awesome game, check it out here. and watch the trailer. ). At some point you just get burned out with a certain genre or franchise. And MetroidVania was having that effect on me. I played Cave Story and put about an hour into it before I said "Ugh, this crap again." and moved on. Same with the other MetroidVania Castlevanias. Same with Metroid Prime 1. I don't think these games are bad by any stretch of course. But on the whole I just got tired of the genre.
Enter Blaster Master Overdrive (on WiiWare) and I'm actually getting into it. For one thing it fixes a few issues the original game had: namely the overhead levels being too long and tedius, the lack of a map system, and the biggest crime of all; no save system and no paswords. I have no idea how someone is supposed to beat that game in one sitting without a guide.
I was expecting a remake of the 1st game and it really isn't. It's an entirely different game when compared to the 1st and 2nd (which I feel is pretty underrated). It's also surprisingly difficult. It's not a cake walk by any stretch and if you don't play carefully you will get wrecked.
I've only put an hour into it but I dig it.