I wouldn't bother with the regional checkbox. there's just not enough information in the rom descriptors to really know what language/country each game came from. We need something like catver.ini, but for languages.
The best thing to do is just experiment.
what you can do is start with a small filter, like no mahahahjonhg games, and nothing with a light gun. Export that list as an XML file, then go into settings and tools and re-load that XML file in as your main input. [caution, outputting XML files can take a long time] Then you can play with different searches and see what comes up. You can always repeat the filtering concept to continue to remove game types you don't want. Heck, you could even do a "search for only clones" and save that list off so you can refer to it later and pull out any games that you recognize from the list. I tend to also do things like filter out games with video resolutions that don't fit on my screen properly.
Check the tutorials for romlister too.
also, some of the clones are pretty cool. For example, I think Piranha shouldn't really be considered a clone of pacman. Yeah, it's similar, but totally a different game experience, so use the clones checkbox with caution.
Oh, and just in case you run into problems, there's a beta romlister where I fixed a hang condition.
http://www.waste.org/~winkles/ROMLister/rl23b.zip I still have more work to do on the next release.