Gamera is filled with meat. We've been eating Gam-er-aaaaaaa
So goes the "Gamera Song" on MST3K. Gamera, for those who are unaware, is a giant flying turtle featured in various movies put out by the Daiei Film company. Though he began as a lower budget competitor to Toho Studios' Godzilla, Gamera has become an icon in his own right.
Gamera first came alive on screen in 1965 in Gamera The Invincible. He found his way to American screens in a dubbed version the following year. Godzilla was already a phenomenon in both nations, and the appetite existed for a second Kaiju for filmgoers to watch. And like Godzilla, Gamera would go on to spawn a franchise that continues to this day, though his career spanned a mere 11 films (compared to 33 for Godzilla) and there have been no new ones since 2006. On the brighter side (for the big turtle), five of the Gamera films have been featured on Mystery Science theater compared to only two for Godzilla. So this should tell you a bit about the relative quality of the movies.
The reason, I think, is that Godzilla went through kind of a goofy phase in the 60s. The films began to be aimed at children more than adults and Godzilla became a protector of the innocent and less of a rampaging menace. Gamera was CREATED in the midst of this period, so while he is a straight up monster in his first film, he quickly becomes "a friend to all children" and a protector of Japan.
It is interesting to speculate on why this is. By the 60s, I think, the memories of war between the US and Japan was fading, Japan no longer felt threatened by atomic annihilation at the hands of the US, and both the US and Japan began fearing annihilation at the hands of the Soviet Union. And both felt the only thing keeping that at bay were the atomic weapons of the US. Thus, the former stand-in for fear of nuclear war became something that protected the people. Protected the children. Plus horror was moving in a different direction from the atomic monsters that were so popular in the 50s, so Godzilla became...well...kind of corny. ANd with Gamera being created in this time, he had those attributes from the start.
Looked at in comparison to the Godzilla movies of the time, though, I think Gamera compares well. The films were corny and aimed at kids, but at the same time, so were Godzilla movies. And frankly, I think the film showed a little more imagination. Kaiju don't really make sense to begin with, they are things that really couldn't exist in the real world, thanks to pesky things like "physics" and "biology", but the makers of Gamera seemed to say to themselves "Well, this is all bullshit, but we might as well have some fun with it". So they did. Gamera's first opponent was a creature called Barugon, a big lizard with a tongue that emitted freeze gas and a horn that emitted a spectacularly deadly rainbow. And they only got weirder from there: Gyaos - a laser beam shooting bat thing, Viras - A giant alien squid, and many others. All much more bizarre than anything Godzilla ever fought, in my view.
Godzilla's and Gamera's paths never crossed, sad to say, though such a thing would be epic. But luckily, we can watch them both in action, and I recommend doing so.