I think neither RMXP nor RMVX have an included feature for that, so yeah... you have a bunch of possibilities to workaround that...
- outline the text with a 1px border, multiply it and shift it around, etc... (all look like shit)
- increase the text size (might not work for the one or other font really)
- modify your font to your needs (requires in-depth knowledge of font editing, and some skill at least)
Since method #2 seems to be the best one for now, I'll explain that to you... go to your Main script (bottom of your script list, I figure you know) and insert this somewhere on the upper half:
You can play around with that, and you'll notice that in RMXP, for example, the Arial font will be regular on 21, but bold on 22... while that's something that heavily annoys me, it might actually benefit you.