I dont like the word choker, but Riquelme was a high maintenance kinda guy who required insanely amount of responsibility for the teams to be built around him, and everything to be based on him doing well or not (very traditional nr 10, from a player who is a rather difficult personality to handle). And yes in that sense, he has been bit of a choker for Villareal and the Argie NT. Not Barca, that was just a normal flop and mismatch of personality and position.
And no, I dont mean he choked a bit for Villareal because of one pk miss onlky, and him taking them far is acknowledged. But generally he faltered in stages where a player truly shows what he is made of.