If you want to go stat wise, are we basing this on legendary or non legendary, Also, I happen to still play pokemon, even though I am 21 It never grew old for me. I am more of a battler and collector however, managed to complete the National Pokedex on Diamond, which is a whopping 480 ish pokemon. Working on the Pokemon Black pokedex, but started to go towards a battling path and trying to raise the best pokemon.
Stat wise my favourite Pokemon Would be Wobbufet as a tank, because his hp rivals that of blissey and he has high defense and special defense. If you make him learn encore when he is a wynaut then you can force the opponent to use the same move again, allowing you to use counter or mirror coat efficiently.
For an all out attacker, I would pick Garchomp, he is the final form gible and is dragon Ground. He can learn fire fang, earthquake, dragon claw and shadow claw. This move set allows him to take down pesky ice types that would target dragon types, and gives him a boost against other types as well. Garchomp has very high speed and attack stats and usually has the ability Sand Rush or Sand viel, which either increases speed or accurary in a sandstorm, so he makes a good partner to any other pokemon that learns sandstorm, or to any pokemon with the sandstream ability.
For max stats, the best pokemon is the legendary Arceus. This pokemon is referred to as the God of all pokemon, and has the highest total base stats of around 750. The next closest is Mewtwo with around 690. Arceus has the ability to change its type based on what plate item it holds, so you can fiddle around with whatever combo you like. Arceus is balanced and can become either a special or physical attacker if you want, and can learn a variety of moves.
If we wanted to go for nostalgia, I would definetly pick Charizard, no pokemon was more reliable for me in the original games then charizard, and even in the new games charizard still can hold his own if raised right and taught the proper moves.
My team I am using to fight in the battle subway in pokemon Black is Haxerous, a Pure dragon Type, Rotom(Washer Mode) Which is a Water Electric type with ghost moves also, and Finally Volcanera, A bug Fire type. I am going to probably swap out haxerous for a garchomp once I can get one by trading, and will probably hatch countless eggs to get one with good IV stats. Also managed to hatch a shiny axew which I trained into a haxerous, and it looks pretty beast.
Overall my favourite pokemon? Dont have one, each pokemon is good in its own way, and I dont really think any are that special. My niece on the other hand has a thing for Celebi and pikachu.