Depends on what you mean by easiest? Easiest to learn and play? To study? Easiest to beat?
If you mean easiest to learn and play, then I don't think so. 5 card draw is really simple, there are only 2 rounds of betting, and no community cards. Much simpler format than Texas
Is it easiest to study? Well that depends on whether we're talking cash, tourney, SNG, whether NL, PL, or limit, and what kind of opponents we're playing. But overall, I'd say no. Easiest to study is probably 5 card draw. Again, there are only 2 betting rounds, you have to calculate simpler odds. And the fact that not as many people play it anymore means you can get more value out of 1 hour of study in 5 card draw than 1 hour of study of NLHE.
If you mean easiest to beat, I would draw you back up to my previous statement. Generally, less popular games are softer because people who play to win go where the most players are (at least online). People who play razz or 5 card draw do so, again generally, because they prefer the format for whatever reason.
I think the reason you believe hold'em is easier is because when you play other games, you are probably the fish. So you lose or break even, or maybe win a small amount, but because you are less experienced in these games, they seem harder. (All of this is a complete guess on my part about your poker experience/knowledge, and of course could be completely off base.)
Also consider the plethora of media attention around hold'em. 90+% of poker shows, topics, hand analysis (at least on CC) are about NLHE. So it's easy to think just it's the easiest because it's basically the only game in town, so to speak.