It's a toss-up between REO, PL, and CDjr, for me.
REO and CDjr were more consistent at overall placements (there's a smaller sample size for PL as well, as he did not attend as many tournaments as those two), but you can't erase the repeat EVO victories argument...that's such a big deal, and he did so over both REO and CDjr. He even won/placed high at the tournaments he did enter fairly consistently, if memory serves correct.
If it had to be concrete, I'd say REO. He was consistent on such a regular basis...it never really seemed to be a real low spell for him...despite not taking EVO, he was top 2 twice, as well. CDjr seemed to wane a little bit towards the end, and PL had a bit more sporadic placement after EVO 2011, but remained effective until the game's end, and has more top 4 placements at EVO than the other two players. Honorable mention goes to DJT, as well. The only knock is he didn't hit full stride until arguably the later half of the MLG 2012 run, but he's still one of 3 EVO champs for the game.