You need to specify what we're basing the pokemon abilities on.
The games'/TCG's mechanics? The lions win. Pokémon run out of HP and/or PP.
The Pokedex? It often contradicts itself and breaks basic laws of physics (the "this pokemon should instantly annihilate all life around itself given its ridiculously high temperature" kind), so..
The game's stories? The Pokémon probably win, given there are literal gods of space and time on their team. (with powers that can canonically rewrite reality)
The anime/manga? Well, that's up to discussion, I guess. Haven't watched/read the stuff with the gen 4 legendaries in it, but I'm pretty sure they just didn't end the plot the first chance they got.