This question is along the lines of favourite emacs shortcut or best video editor or text editor or php/ror editor for ubuntu. Many of them are lingering along nicely as community wiki's without accepted answers capturing the opinions and suggestions of the community.
Compared to editors, games, IMO, may not even incite so much flame-wars and would rather educate on the variety and options avaialble. Most of us have a single text editor we can't live without, with games on the other hand the more the better I guess.
Finally, the fact that there is IRC or forums shouldn't mean people should go there instead. For me, it is natural to aspire for the google search for favourite ubuntu games to also land in askubuntu.com.
I agree it should be community wiki, but not something deserving to be closed. Is this some new rule we have taken to up to ban all questions that invite such opinions ? Aren't we being too harsh here ?