I think Rock Band will be the better game because Harmonix (makers of all Guitar Hero games) is developing it. However, I don't think it will sell as well as Guitar Hero 3 because of the price & release date in comparison, but it could do a significant % compared to GH3 sales. If GH3, which is now being made by Tony Hawk developer Neversoft, somehow turns out really bad, I could see RB outdo it in sales, but this is unlikely because it would be really hard to screw up what Harmonix already put in place.
The casual crowd will buy up a lot of GH3 sales, while the hardcore will go for RB, and probably partner with their buddies to make a band. I think they can coexist to some extent, you'd think the sales would then not be good enough for both games to continue, but this is a genre that both Activision and EA probably want to grab as their own so future entries in each game are probably very likely(If RB bombs though, EA will not go for the full band experience sequel). Not to mention people will already have the peripherals by then. You'll likely see Activision try to make future releases move beyond just guitar (if RB does well), unless they want to maintain a guitar fanbase only because they see RB's strategy as too risky+costly. If ATV do move beyond just guitar, RB will be a step ahead by then because the peripherals will already be in hands of consumers, Harmonix is the developer, and RB will have been known as the full band game.
If RB bombs, ATV will likely make RB's guitar compatible with GH4.
GH3 will get more sales in its early months than RB, but RB could have a longer tail. RB does support GH guitars.
We may also see different music games in the future that utilize even different instruments or a developer will again take a cue from Konami (Beatmania)...
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The casual crowd will buy up a lot of GH3 sales, while the hardcore will go for RB, and probably partner with their buddies to make a band. I think they can coexist to some extent, you'd think the sales would then not be good enough for both games to continue, but this is a genre that both Activision and EA probably want to grab as their own so future entries in each game are probably very likely(If RB bombs though, EA will not go for the full band experience sequel). Not to mention people will already have the peripherals by then. You'll likely see Activision try to make future releases move beyond just guitar (if RB does well), unless they want to maintain a guitar fanbase only because they see RB's strategy as too risky+costly. If ATV do move beyond just guitar, RB will be a step ahead by then because the peripherals will already be in hands of consumers, Harmonix is the developer, and RB will have been known as the full band game.
If RB bombs, ATV will likely make RB's guitar compatible with GH4.
GH3 will get more sales in its early months than RB, but RB could have a longer tail. RB does support GH guitars.
We may also see different music games in the future that utilize even different instruments or a developer will again take a cue from Konami (Beatmania)...