In terms of support and listening to their fans, Bungie are probably leagues ahead of IW. Plenty of people complain about a vast amount of problems in MW2 yet they go unfixed.
Still as far as the final shipped (unpatched) product though, I think MW2 is a superior FPS experience to Halo 3. MW has brought about some nice changes and innovation to the FPS genre. Games like MAG and Resistance 2 have both used a similiar experience counter to MW, and honestly, I can't picture myself playing a FPS down the line that doesn't have customizable killstreaks to reward the player.
It's a real pity IW fell apart, MW3 could have been even bigger and better.