I haven't seen Gundam Age (or really any Gundam to be honest), but I will say that Gurren Lagann is fantastic. Personally? It's my favorite anime of all time, and I've seen a pretty decent share of mecha.
Gurren Lagann, while appearing to be a simple, Shounenized mecha story, ends up being a lot more than that. It starts off seeming a bit generic, but when things kick in, they really kick in. The action is fantastic, the character development (particularly for the main character) is amazing, even the themes of the story are great. In spite of how mindless the series appears to be (and how much the protagonists shout about ignoring logic), the story actually has a lot of life lessons and does tread on some moral questions. Definitely not to the level of something like Death Note or Code Geass, but the circumstances and actions of the antagonists are pretty thought provoking.
Don't wanna pull shameless advertising here but I've written a review of Gurren Lagann that explains in more detail why I found it to be so amazing:
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That would probably do a better job of showing how awesome Gurren Lagann is than whatever I post.
Gundam is much better. Gurren lagan sucks!
Please tell how an anime with hardcore action, amazing character growth, thought provoking themes, fantastic production values, and a very memorable OST "sucks." Because whether we're judging on an objective or subjective basis, there are very few things about Gurren Lagann, if any, that "suck" and I hope you're capable of giving a decent explanation about why you think that.
And I can't be sure since I haven't watched Gundam myself, but I've heard very poor things about Gundam Age in comparison. Gundam Age has a 6.76 on MAL, which causes me to question how good of a series Gundam Age can really be. While a lot of the other Gundams are scored a lot higher (and probably ARE a lot better to begin with), the fact remains that I'm very skeptical about the fact that you'd laud Gundam Age and yet bash Gurren Lagann, without even taking the time to explain why.
