I will admit, I though Microsoft would have given up after the first Xbox's performance. I loved the HDD, and what they did with Xbox Live, but except for the Halo and Splinter Cell games, it never interested me in the least.
Fast forward to the present and they have blown me away with what they've done with the 360. The only reason I don't own one is because I can get everything I care about (and the exclusives I prefer) on my PS3, however, that looks like it could change with how great Halo 4 looks with its Metroid Prime-ish influence to the series.