Well, one of the sources for the "power creep" in OU is that there simply are more Pokémon now than before. The group of the 5% strongest non-legendary Pokémon in the game is getting bigger and bigger, with move- and ability-pools expanding even beyond that. Brought back a couple of generations, I think a current RU team could wreak havoc in the upper tiers of an earlier metagame. As a rule of thumb, the strongest non-broken Pokémon in the game make it to OU, and as the general power level of all Pokémon increases, so does OU itself. The metagame becomes more fast-paced and hard-hitting than before, while the middle or lower tiers adopt the playstyle and power level of the previous generation's OU. The bar for competitive playing is raised a little bit for every generation. Last, I think that the average power levels of all Pokémon in relation to another might not change much from generation to generation, but the few % at the ends of the bell curve embraces an increasing number of 'mons. Just as strong Pokémon, moves and abilities are added in every game, so are crappy Pokémon, moves and abilities. In total, it evens out, but as we tend to concentrate on the strongest few percent, to us it appears to be a radical power creep going on. It's easy to forget that we get a Vanilluxe for every Hydreigon and a Zen Mode for every Regenerator. Gen. V Beedrill would completely smash the Gen. I metagame, but in Gen. V, it's still residing on the bottom of the barrel. I think hardly anybody bashes a relative power creep in NU.