Of course Stan Lee is a playable superhero.
There is a ton of content in LEGO Marvel: more unlockable characters than ever before, bonus stages beyond the scope of the story, and a city dense with collectibles. But, the downside of this breadth of content is a relative lack of depth -- rote missions, a repetitive world map, and mechanics that get reused across much of the game's cast (Wolverine and Beast, for instance, are effectively identical).
The game does more right than it does wrong; it's certainly enjoyable to ride the story and bonus missions through to completion, and even to uncover the rest of the game's poorly-hidden secrets (if you're into it, which I definitely am). On its own, LEGO Marvel is pretty great. But in the shadows of LEGO City Undercover, which had more interesting writing and a wonderfully varied landscape, and LEGO The Lord of the Rings, which paid impeccable (if sometimes parodic) respect to its source material, this installment simply can't measure up. Everything just feels more samey than those previous LEGO adventures. (It doesn't help that almost all of the male NPCs are played by the same three dudes.)
Of course, it might just be because I'm not a Marvel superfan. If you've been waiting for a game that let you play as Iron Man, the Silver Surfer, Wolverine, Dr. Doom, and Mysterio - et al - this one's clearly for you.
Better than: LEGO Batman 2: DC Super Heroes (3DS, Mac, PC, PS3, Wii, WiiU, X360)
Not as good as: LEGO City Undercover, LEGO The Lord of the Rings (Android, iOS, Mac, PC, PS3, Wii, X360)
LEGO Deadpool doesn't do much: but LEGO Stan Lee can web-sling, laser, and hulk-out, so, yeah.
Progress: 100%