Here's an example of a classical tune that I think is very catchy to illustrate what Austin_4e said (Dvorak's Salavonic Dances):
But I don't think that this is what people complain about, it is catchy but it still sounds like an orchestra, it is very much a classical music. I personally don't mind that it is. But I think that this is what some people don't want. On the other hand, I don't find that Rayman sounds like classical music at all (and definitely nothing like Mozart or Beethoven for someone who suggested that), it is much more exotic with some instruments rarely used in classical music (it even features electric guitars at some points...). And those people still say that it does sounds like classical music, so I'm not sure I understand them afterall.