It's kind of hard to see most of Animated or Prime benefiting much from a Masterpiece treatment. Apart from maybe Lugnut or Knockout.
Beast Wars depends on the toy/character IMO. I only have Cheetor, not interested in Optimus Primal because I'm happy with the Transmetal one. I'll skip on Dinobot too, though I do think it looks nice - I just like the Transmetal 2 design better, and like Dinobot as a villain for the Odieverse. But damn if TM2 Dinobot couldn't do with a better toy. Rampage and Depth Charge are fine as is, but I could really go a TM2 Megatron - in fact it's my Number 1 most-wanted MP, not that I think we'll ever get one. Voyager Rhinox is good enough for me, but I would probably upgrade to an MP if/when they make an MP Rhinox. I'd also be all over an MP Beast Wars Ravage.

About the only 'really good' toy I would like to see an MP of is G2 Laser Prime/Black Convoy/RiD Scourge. The toy still holds up just fine, but it's such a nice, solid design with good play- and display options that I reckon it could make for a good Masterpiece as well.