The DS requires purchasing a DS flash cart, something you can't just walk into Wal-Mart and buy. The DS is suffering not just because of piracy but also (IMO) because of the growth of iOS. A lot of people are using an iPod touch for gaming (or buying one for their kids to game on) rather than using a DS (or buying one for their kids)
iOS piracy isn't rocket science either (in fact, IMO its just as easy to jailbreak an iPod Touch as it is to pirate for PSP) and that platform is still going gangbusters with no signs of slowing down. (including games from the big names in gaming)
As for Wii, it was never going to get the range of AAA mature titles that the PS3 and 360 get (and Nintendo never pushed it that way) but it IS getting top tier titles (e.g. Rock Band, Guitar Hero, sports titles from EA and others.
Piracy didnt kill the Dreamcast, the Dreamcast was as good as dead before it even hit the shelves (both due to the flop that was the Saturn and because of the imminent release of the PS2)