You should
watch these videos to get a feel of what the Pokémon series is like, although normal gameplay is nowhere near that.
(WARNING: Will spoil the entire games.)
Also, check out
this site for general information about everything Pokémon, and
this site for how to win in Pokémon.
The Castlevania games for the DS are very well made, and very fun to play. If you like playing a sword-wielding blue mage and don't mind the "Magic Seal" crap that they force upon you, play
Dawn of Sorrow; if you prefer some more classic Belmont whip action, play
Portrait of Ruin; if you want to play a genuinely hard game (and also as a woman), play
Order of Ecclesia.
And if you've ever played FFTA for the GBA, you'll feel right at home with FFTA-2, although some battle mechanics have changed.
Also,
Contra 4 WILL make a
MAN out of you.