Difficult question. There are a lot of different fighters who have showcased good boxing skills. Aldo is certainly one of them. Alvarez has some skills which are very admirable, and some which aren't quite on that admirable level (though, he has moved to sort out some of his flaws). I have liked what Cain and Cormier have done at times. Their boxing coach has educated them on the fundamentals. Both possess a trustworthy jab (to the point where they both outjab essentially anyone they fight), and they both move their head on a basic level. Neither wholly neglect body punching, either. That's a few, anyway. There are more, of course.