Mmm, no i don't think the 360 is worth purchasing to get Those, when a), i have oblivion on my PC + expansion packs if i want them b) a $300+ console in order to get a $170 game? No thank you, c) Halo is great. But i don't want to spend $400 just to play it. Not to mention i'm spending money every month to play it online. If i got everything on there, i would be spending, oh $650+. not to mention downloads fo rockband and XBL. Or i could get the wii with wii sports, brawl, prime 3, LoZ:TP, and mario galaxies, all of which i enjoy and love, for $450. Without additional expenses(i'm not looking at controllers for either system). I have 5 games, all of which are exclusive to the wii, two of which have multiplayer that's addictive and fun, one of which has free online. for $200+ less.
Now i know this contradicts what i said before. But i just feel saying a console is worth buying for just three games, one of which is $170, another of which i will a) eventually not play again, (though it does have quite a long lifespan) and can buy $10 cheaper for the PC with mouse control. If i bought a 360, it would not be for three games. since i have the option, i'd basically be buying the 360 for two games. sorry, but that's not worth it.
now buying the 360 for those two AND the rest of the huge library it has to offer is worth it. I mean, it's the same with the wii, like you said. If someone bought the wii for like mario galaxies and smash, it would not be worth it, when there are still plenty of games to check out.
edit: wii now has downloadable content announced(paid for). SO it looks like rockband wii will most likely have dl content.