I liked Sam and Max from the beginning. I played it for the first time when I was 10 years old and my English wasn't that good. A few years later I liked the game even better. That's because my English got better and lots of it's jokes rely on speech. Sam and Max use quite an arsenal of strange words.
Also, a lot of jokes are only funny if you know certain American facts. American pop-culture, if you will. It wouldn't surprise me if most people who dislike Sam and Max are from other regions then the US.
--Erwin