Halo 3 certainly sells more initially, and likely sells more overall. SSBB has a better chance of over coming Halo 3 than SSBM had with Halo 1 or 2, but if you're expecting a hardcore game to much better than ever before on the supposed casual console you need to think about what you're saying. Brawl has a chance, but the cards are still in Halo 3's favor.
You do not have the right to never be offended.