I don't think it's fair to compare the two. At its core, SSB:B is a 2d fighter, while LBP is a 2.5d platformer.
SSB has the nostalgia bent, one that LBP can't come anywhere NEAR(Sony just doesn't have the catalog of characters Nintendo does, mostly because they haven't been in the industry as long)
LBP is highly focused on user-generated content, something few games on any platform have even experimented with and even fewer have made a major focus. The stage editor built into SSB:B is essentially a set of wooden blocks compared to LBP's Lego technic set.
Sales wise..... Given the PS3's current user base, I don't think it will match SSB:B, even if I think, from what I've seen so far of LBP and after playing an extensive ammount of SSB:B, I'll enjoy LBP more than Smash.







