Here's my review. And yes, unfortunately I spend a little money to get the heroes I want.
The short version: "Meh" It's not a specific failure in any one category, but at best it's mediocre. Add up a bunch of mediocre score and you get "Meh"
Honestly, they probably would have been better off not firing the Champions Onlines guys. That game wasn't great, but it was more fun than this. And with Marvel IP backing it, it probably would have lasted much longer before being sold to a Korean grind-fest company 1-2 years ago.
A) The gameplay mechanic is... a mixed bag. On one hand, it's Diablo-centric. On the other hand, it's less "fun" than even Champions Online, let alone DC Universe. City of Heroes was an epic game for its time, and even with its primitive mechanics it was superior to this game's point-and-click, point-and-click. No targeting is given so teleporting-bosses are annoying. Heck, I would have LOVED an XBox controller a-la the various XBox Marvel games.
B) Stories and missions are... not enthralling. DC Universe set the milestone for mission "text." Instead of boring walls-of-text, they had voice actors tell you what was going on (as well as offering the transcript). It made it much more engaging.
Marvel Heroes? Like 2 lines of text at the bottom of the screen saying "Go get the macguffin" or "go save <person_x>" Seriously, lame. As bad as Champions Online was in this regard, they at least gave you some funny stuff buried in their text.
C) Customization = FAIL. OK, I get it... they pigeon-holed you into picking a pre-existing hero and one of their pre-created costumes. But I just don't find it that engaging playing a cookie-cutter hero.
I'm really into comics and have a handful of "heroes" I've imagined: names, backstories, costumes, power sets, etc. I take it a bit far, but I guess so do some D&D players and such. Seriously, comics are my bag... I have a couple grand worth of comics (physical and digital).
So... while I guess it is nice playing as Iron Man from time-to-time... it's not what I want long-term.
D) Hero clones... this kind of goes along with C) but playing as a pre-built character is mildly annoying. Watching 10 of them on the screen at the same time is horrible. It really breaks any immersion you have what-so-ever if you are wandering a map and stumble upon like 2 or more of your characters.
I realize they have a story-reason for this... but it's still lame.
E) It's not as "Pay to Win" as people *itch about. The "pay" gives you either an XP-point booster for an hour, a rare-loot-drop-increase for an hour (which really does nothing), and a couple of pets to help you out if you need them. And of course, unlocking other heroes and their costumes.
It's not like you're buying powers or leveling up much with that stuff. It's not like you can by "The Sentry" or "Hyperion" and have an uber-hero instant-win or anything.
F) The heroes are... balanced well enough. None feel particularly OP compared to the rest. So going along with E), it's not like there are any must-have heroes to win the game easier.
All in all... for a FREE game (assuming you can live with the limitations) then have at it. If you like Marvel and you miss Dioblo point-and-click combat then it's not too bad.
But, it's meh.
"Space. It seems to go on and on forever. But then you get to the end and a gorilla starts throwing barrels at you."