Hm, guess it's time for a semiformal ruling.
In general I wrote the 'don't nominate the same game' rule for two reasons:
First to avoid one game dominating - not necessarily because HOI or EU are more popular so much as a winner would probably tend to read the same games he writes about, and that could easily turn into a trend.
Second because the awards like this were, I believe, meant to encourage the general Paradox community which includes all the games.
That said, the 'rule' has certainly fallen before, and none doubt 'Fire Warms...' is worthy of recognition. In your shoes I'd choose an AAR from another game, but I'm not going to whine if you'd like to go ahead with a Vicky submission.
Regarding 'Fire Warms...' winning so many accolades: I agree it has, and I'm also of the opinion that the 'Showcase' is better at highlighting and drawing attention to new entries in AARland, but on the other hand that's not a requirement nor stated anywhere. If I recall correctly another AAR's won twice, and certainly 'Writer of the Week', which is also good at highlighting newcomers to AARland, has had plenty of people win twice. I'd say if the only thing stopping you is 'Fire's' past popularity...don't let it.
In general, pick a submission you're comfortable with. If it gets to the point where I think we need to let the Showcase wander elsewhere for awhile I'll pipe up.
EDIT: For anyone interested, the master list on the first post is updated. I see EU2 won something like 5 times in a row, then HOI twice, and now Vicky twice. *grin* I wouldn't worry about Vicky getting too much attention.. Go with an AAR you enjoy!