The more I think about it, the more I think an all-fictional CB would be an exercise in futility. I can't see anybody above say, Yoshi, losing to Batman. Maybe it's just me, but I don't really care for any fictional VG characters that we haven't already seen.
It would have a decent mid-tier competition, but this site is first and foremost a gaming site, and that will only get more and more apparent as the years go on.
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Game of the Decade? More like Guru of the Decade mirite?