If you ask any professional developer (indie or otherwise) I'm sure you'll find that there is no "Best Game Engine". There are always +'s and -'s when you talk about any game engine be it Unreal or Torque.
So for now what you want to look at is the "Best Game Engine" for your purposes. Which means evaluating things like:
1) Is the engine primaraly a FPS engine? If so then making another type of game such as a RPG or third person action game with it might not be feasable due to design decisions made.
2) Features. If you plan to use HDR and the engine doesn't support it...well you can see where this is going.
3) Support. The game engine you are using either needs to have support via it's developers or through a well established community (no startup engines here). Otherwise how are you going to get questions answered?
4) Tools, Your looking for an engine that has plugins for the modeling program you use, particle editors, ect. Buying an engine that only has max plugins is useless unless you actually have 3d studio max. Other tools for the engine itself help with your development/prototyping pipeline, if they suck then people are going to get frustrated and say "This engine sucks".
In short the best engine is what works for your needs.