We have all played them at some point or another. Guitar Hero and Rock Band are beyond household names; they are worldwide commodities. I haven't had the chance to really sit down and play every single song on Rock Band, but I could most likely beat you at GH.
Braggadocio aside, my roommate that owns the 360 upon which I rock has recently moved out of the house, taking all of the plastic instruments with him. Now if you would have asked me a few weeks ago if I would ever miss these games, I would have quickly responded 'no,' but in these last few weeks of their absence, I have found my fingers itching to tickle some frets. I thought about it for awhile, and decided that these games were probably worth owning in some incarnation or another.
Now upon further inspection of all of the different versions of the games, I have found that it is almost irresponsible to purchase any of these games for the Wii, which happens to be the only next-gen system I own at this point. Not only does the Wii version lacks the digital audio and high-definition video of its MS and Sony counterparts, but also (and most importantly in my opinion) any form of downloadable content. This, in essence, makes the Wii version of the game almost identical to the PS2 version, and to top it all off, you have to pay 10 extra bucks for the Wii version of GH:Aerosmith.
I can't imagine owning Rock Band for the Wii only to hear stories about all of the AMAZING songs that my friends downloaded on their vastly superior consoles. Why would you ever limit yourself to the tracks that come with the game? If ever there were a justified reason to spend money for DLC, I would say that complete downloadable albums (such as the new Metallica album) certainly fit the bill.