I'm not sure 10 "top" games were ever made for the system.
But my guess as to the top games are:
1) Zenki FX
2) Battle Heat
3) Langrisser FX
4) Zeroigar (pretty good, if not that advanced really)
5) Last Imperial Price (kind of lame but good animation)
6) Team Innocent (high production values, but borring as hell IMO).
The thing is, the PC-FX is a romantic system because of it's goals and potential. That's how I view it. It is not a "great" system because there are a ton of good games for it. Honestly, I don't think it's full ability has ever or will ever be seen.
If there could have been just ONE game for it as cool as Treasure's Guardian Heroes for the Saturn, or like, Capcom's Dungeons and Dragons arcade games... that would have made me so happy. I'm sure it could pulled off games like those. Or a really good fighting game. Not Battle Heat. Though it's good, I'm talking about something like Darkstalkers.
Hell, even some PC Engine Duo games look more advanced than any of the PC-FX games, and that's kind of sad. I think there's nothing for the PC-FX that looks one little bit better that Lords of Thunder or Valis 3, save for the liberal sprinkling of TV-Quality, low budget animation, which technically the Duo wasn't capapble of, but one asks oneself, "So what?" I'd rather see well drawn static graphics than bad animation.
I say all that but then I turn around and tell you I love the PC-FX? Well I love the potential, and the rarity, and the fact that it looks badass. That's about it.