I've also never seen an RPG where a frog turned into a prince after being kissed by a fair maiden. I suppose that wouldn't be cliche then.
Please focus.
I said it was LESS of a cliche in this context, not that it was not a cliche at all.
I think your example is misleading in a couple of ways. First, if there is anything that is cliche about RPGs, it is their medieval fantasy setting. Putting a prince kissing a frog into an RPG setting is pretty much piling cliche on cliche. Second, prince kissing frog fairy tales are centuries old — they are more mythologic or archetypal than anything. Alcoholic down & outer has been an overused character in a dozen films lately. Not really on the same level.
Here's a more apt illustration. What is the most cliche aspect of RPGs? I think it's the Tolkein boilerplate — the wizard, dwarf, human, and elf characters in a medieval fantasy setting. Big-time cliche, right? Now suppose you had a TV soap opera with dwarves, elves, and wizards, and it took place in a medieval fantasy realm. Would the people watching it say, "Oh, what a boring cliche, I've seen that so many times, yawn, how boring." No, they'd be saying, "What the hell is this? Where's my Days of our Lives?"
See? Genre or medium matters. Something that's old and worn out in one genre/medium can feel somewhat fresh (or less cliche, if you prefer) in a medium/genre that hasn't overused it. In fact, that's where a lot of "originality" comes from — borrowing concepts from other genres and media.
Here's another way to look at it. An alcoholic down & outer is not "special" in some way (unless this aspect of the story is yet to be revealed). This goes against the usual grain of an RPG, where you play a character that — though underpowered in the beginning — is "special" in some way. They have special powers; they are the long-lost hier to the throne; they are the son of a famous scientist; they are a prisoner destined to free the world; they are the last in a forgotten line of whatevers, etc. From this perspective too, a down & out alcoholic is less cliche in an RPG setting than in the films you've apparently seen one too many of.