Is it considered unrealistic for there to be humanoid aliens? I would think there would be a pretty good chance that aliens that evolved in a similar environment to ours would evolve to look similar to us.
Oh, that's very unrealistic. Lots of Earth species have evolved in similar environments and haven't ended up looking anything like us. Even granted that technological species have a reasonable chance of being two-armed bipeds, they could just as well end up shaped more like a velociraptor or a kangaroo than a human. And there's no reason other body plans couldn't work too. The most intelligent species on Earth other than humans and our sibling apes are: Elephants, corvid birds, cetaceans, and cephalopods. There's enormous variety there. And elephants occupy much the same environment as primates, yet their body plan is profoundly unlike ours. Ditto for cetaceans and cephalopods -- both ocean-dwellers, both competitors for a similar niche (whales and squids are mortal enemies), yet astonishingly dissimilar to each other in body plan. And that's just on one planet and based on one genetic code.
No other order of life on Earth has evolved to match a human shape, so it would be even less likely to happen on a completely different planet. Sure, we like to make up arguments about how our shape is the "natural" shape that intelligent, tool-using life would tend toward, but the fact that we've found intelligence and tool use among elephants, cephalopods, birds, etc. pretty much debunks that. It's a human habit to expect ourselves to be the center of all things, but we've always been wrong about it before. We weren't created in God's image, the planet wasn't created for our benefit, Earth isn't the center of the universe, the Solar System isn't the center of the galaxy... now we even know that our planetary system is actually an oddball rather than a typical system, that it's unusual to have all the rocky planets near the Sun and all the giants farther out. We should've learned by now that when we expect ourselves to be the template for the universe, that's nothing more than ego.
Indeed, the human shape is actually far from ideal. We're shaped the way we are because we're a bunch of tree-swingers still in the early stages of our adaptation to walking upright. We haven't even come close to evolving into a perfect form for upright locomotion, which is why we have so much trouble with bad backs and fallen arches and even hemorrhoids. We're in transition, betwixt and between, still only half-adjusted to our niche. Which is probably part of why we've needed to invent technology to compensate for our many physical shortcomings. Other intelligent, tool-using species might well be similarly ill-adapted and half-evolved, but the odds that they'd happen to share our particular misfit attributes are quite low.
And sure, it's a big galaxy, and there are probably a few planets where a shape roughly similar to ours has developed. But they wouldn't be so identical that they could be replicated by sticking pieces of latex onto a human's face.