I don't think I can pin down a Top 5, but I'll explain the various Pokemon I've used on my main-series teams, from my first to my most recent.
#1- Swampert
Named: Lieutenant
Obtained: Starter
My very first Pokemon game was a copy of Emerald someone let me use for a tournament everyone...
Okay, okay, I admit that that isn't the most imaginative or inspiring title of a thread you've ever seen, but it gets better.
Alright, so that fan idea of "let's create a game with all the regions" is absolutely never going to happen in any official release. No way, no how. GameFreak would...