There's no beating his appearance in Infinity War. The CGI is just superb. I liked how he looked in GOTG and the AOU post credits scene as far as comic accuracy goes, but I prefer the real eyes of the IW Thanos. They give him more depth than the blue glowing eyes. As for his first appearance in The Avengers, I even knew back then that was only a prototype version of Thanos, but they seem to have went back to that version's skin tone for IW. Either that or it was just a lighting thing in GOTG and AOU.
As far as his outfit goes, when his Infinity War look was revealed, I wasn't a fan of the tank top at first. I thought that he should have his armor on at all times and that he looks like he's going to the gym instead of going to war. But it really grew on me. I do like his armored look, both in GOTG and IW, but I also like how the more stones he acquired, the less he felt the need to protect himself since he was gaining all the power he needed in the gauntlet. That being said, I wouldn't be opposed to seeing him armored again in Avengers 4.