He's mostly considered a joke character amongst the MK fanbase, even after Netherrealm Studios have went through the trouble to add a great storyline for him. But alas, some people are just ignorant and can't look pass the fact that he is purple and is called Rain... Purple Rain, by Prince... Yup, that's how he got his name to start with. I see him as having evolved pass that though and turned into an awesome character! Especially in the newest MK!
Well, add in the fact that he's an Edenian prince, too... lol But yeah, he's awesome. He did used to be a joke character though. Someone shown in the demo mode of the game but not actually playable.