Halo selling better than Metroid has little to do with marketing and more to do with everything about the games.
Halo is (was?) cool. Fresh. New system. Awesome, mysterious title. New concept. Not to mention the game was amazing and groundbreaking. It was the first first-person shooter that truly drew me in. I was in university at the time, and playing co-op campaign was awesome. The 4-player vs was great. So many inovations...the regenerative health... the vehicles... the bizzare ring world....it gave me a gaming feeling of awe that I hadn't seen in i don't know how long. Maybe since I first saw Super Mario Bros on NES.
Metroid is dorky. The name sounds funny. Very Star Trekkie sci-fi. It takes lots of exploring and thinking. No co-op, no multiplayer. It's a slow paced adventure. Great game, but nothing like Halo in any respect and it didn't re-energize my love of games like Halo.
