Gears 3 will outsell Gears 2, seriously. Gears 2 only did so "bad" because the multiplayer was pretty much unplayable except locally. When Gears 1 came it was the only great online game for 360 that was not Halo 2. Gears 3 will have dedicated servers, this alone even if the MP would be the same as Gears 2 MP is enough for some (myself included) but it also has 4 player co-op and probably a great campaign.
UC3 will probably do well, but i don't see how it will do better than UC2 when UC2 was bundled. Maybe UC3 will also be bundled, but PS3 slim was fresh when UC2 came. Now not many people will pick up the console for 1 game, if it is bundled though, it will sell well, maybe better than UC2 but not better than Gears 3. And if its not bundled there isn't even a competition.
