Who can tell? There are exceptions to every rule. Some games (Tekken 6) were big names and flopped when they went multi-plat. Other games were exclusive AND hyped and flopped, too (Too Human). There's no way to tell. Dead Rising, Saints Row, Lost Planet, BioShock --they've been pretty successful as exclusive franchises. Even if they were multi-platform, they would be or have been hit games. Ninja Blade and Lair were exclusive, but nobody gave those games a second look.
The biggest factor is quality, I guess. If Call of Duty is a good exclusive, it would be a good multi-plat. At the same time, I don't think inFamous or some other games would have gotten as much attention if it weren't exclusive.
What I'm trying to say is, I have absolutely no idea.
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