If you really want one, you can find working N64s or Dreamcasts on eBay, often with bundled games, for much less than $40.
As for the rest of the OP's questions:
1) Don't pirate. It's illegal.
2) Blast Corps seems to go for about $2-$4 + shipping on eBay, so no, it's not expensive at all.
3) For the N64, most of the good games are FPSs or platformers, with the occasional good action-adventure (i.e. Zelda) or RPG (Ogre Battle 64) thrown in. For the Dreamcast, you really need to like quirky, genre-defying games like Jet Grind Radio, though there are a lot of more "traditional" games as well.
4) If I had a choice between N64 cartridge or VC, I'd pick the VC. N64 games on the VC are upscaled to 480p, meaning that they look sharper, and the colors look more fleshed-out.
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom
