I took an English Lit class. In ninety percent of the literature that we read, the main character died (I normally make a point to distinguish between the MC and Protag, but in this case, I'll let myself slide). It became to be known that our class revolved around "death and shopping." (In several of the works we read, the characters were also rather materialistic, hence the shopping (see A Pair of Silk Stockings, Araby, Paul's Case, etc.).
To make my point, the happy ending is new, not the bittersweet or sad. After all, some of the first literature pieces ever were the greek tragedies. In most of these, the protag dies. In the few that don't, such as in Oedipus, he simply gouges his eyes out (don't worry, he dies later). If the right place to go is your character hitting the big Koopa in the sky, don't let Disney stop you.
-giusti