User-generated Flash content plus user-generated reviews... that's still a really difficult ranking proposition.
Sounds like you're very tech savvy. You should be measuring user engagement on your pages, and cull the pages that users don't seem to like. Also, be careful of any empty pages.
I think that categories and community in a site like this are both very important towards making it work.
Engagement with your Flash content is essential, since the search engines really can't see the content. There are some amazingly good Flash game sites on the web... but they're usually the product of brilliant designers.
Frankly I'd do more than rewrite some of the reviews... I'd also add short text intros to the pages that need them. If the site's in English, you probably need a native English speaker to do some writing.
But it's user engagement that will make or break the site.
You might use social sites like Twitter to let your community know when you've got, say, a new game... and you also need to give your community lots to do on your pages. You need to come up with some really creative solutions, targeted to the kind of audience that you have, and then do everything you can to promote it.
Re linking and Penguin...
...You've got to be very careful about the kinds of motivations you give users for adding their Flash creations. One problem you can run into with user-generated content on a site like this is that some users will try to build backlinks to their own stuff, and this can get very spammy. I'd be curious if anyone has thoughts about how to handle this problem.