your point that the premier league doesnt seem to get the very best players might be true. but what is undisputable is that the average salary of a senior premier league player on avergae is much higher than la liga.
but going back to your point on the very best players, ie. messi and ronaldo. i think in the premier league, its almost impossible for players to post the kind of goals stats that those two get. in spain, messi and ronaldo get hatfuls against teams that are championship standard. the competition is too intense in england for an individual player to do that imo. therefore, a player playing in england will be at a disadvantage in terms of getting the global recognition that top spanish players get, as he simply cannot post stats like 40 goals in 40 games, whilst playing in england.
and although messi and ronaldo havent played in the epl at their prime (i would argue, ronaldo kind of did), i don't agree that the likes of falcao, rivaldo, shevchenko haven't. for me the following guys are at the shevchenko level in their respective positions and played in the epl over the past decade:
rio ferdinand, john terry, lampard, gerrard, scholes, beckham, thierry henry, van nistelrooy, roy keane, vieira, pires, bergkamp, drogba, carvalho, giggs, rooney