It's incredibly financially successful, and has done well with its marketing program. It's also an easy game to pick up and play, but it gets old a tad quickly which is unfortunate because it has very good mechanics. For me, I personally don't like the weekly caps they do, but to each their own.
And although is has been financially successfully does not equate to everyone being happy with the content they were given and the way future content is being doled out by Activision and bungie