I prefer WFC, the robots look great, smooth controls, good story, it recaptures the G1 feel while adding a modern touch and multi-player is great, especially Escalation.

I liked the Armada game but it got a bit boring for me, though the graphics were pretty sweet for it's time.

ROTF actually had some surprisngly fun multiplayer I still go on every once in awhile even now, but the rest of the game was kinda meh.