I think the quality of the industry would suffer if exclusives were gone. I remember something along the lines of "Innovation walks hand in hand with competition". Exclusives are essentially that innovation, giving one product an edge over another. A removal of exclusives would mean that high-quality exclusives would become mediocre multi-platforms, with developement times increasing as the dev force is divided, leading to games that vary in production quality according to which console it was on (similar to apparent gameplay problems on the PC port of GTA4).
I've noticed a few people wanting the three first-party companies to develop some kind of "super-console". Whilst wishful thinking should be promoted, such an idea could spell the start of an oligopoly, as all game devs would produce for just that console, removing competition and thus removing the incentive to innovate. This lack of innovation could lead to a bad spell of uninspireing games.
By the by, I don't think no exclusives would necessarily mean no fanboys. I can tell even now, before the 8th gen of consoles are on shelves, someone is going to claim that the one he preordered is going to be better than the one some other bloke is getting.