Just like straight girls can tell when another girl is hot, can straight guys tell when another guy is hot?

It depends on the guy mostly. Some guys out there compliment other guys on how they look and not feel like they're hitting on them. I think it's a fear of feeling/getting called homosexual if they do.

but like I mentioned, it depends on the guy himself.

a MAN comfortable with his sexuality, would compliment another guy.

But most guys just feel like if they say something like that to ou about another guy, its an automatic gay stamp. >_>

I think the majority of straight men don't really look at other guys that way and if they do they just keep it to themselves. In some cases some act like they don't see it at all usually out of jealously. But, of course that's not all straight men. It's just that woman tend to be outwardly affectionate ou critical when it comes to appearances than men.