Halo 3 in my opinion, it's a good game but it really didn't warrant a huge advertising campaign, launch parties and the live-action virals.
On that note despite how much I love the Resident Evil series, RE5 suffered from this as well and was definitely overhyped, plus pretty much every trailer out there spoiled all the the games cutscenes which was a shame.
On that note despite how much I love the Resident Evil series, RE5 suffered from this as well and was definitely overhyped, plus pretty much every trailer out there spoiled all the the games cutscenes which was a shame.