The others are all less good than GaoGaiGar and few are translated completely. So it's mostly a matter of what you like to see.
I would wager Da Garn is the best of them since the ending is completely amazing. It had the same writer as GaoGaiGar so the show's plot is very good once it heats up. It has a lackluster OP / ED so fans tend to pass it over, but give it a chance.
Exkizer and Fighbird are more episodic. Fighbird is the more enjoyable of the two though its quality fluctuates a lot from episode to episode. Ezkizer has a lot of comedy and is generally more silly, more of a kid's show.
Might Gaine is kind of halfway between Da Garn and Fighbird. It sort of has some plot arcs but they come into play erratically. It launched a lot of major 90s seiyuu which can make it an interesting historical watch. The ending is really interesting as an expression of the eternal tension between toy sellers and show creators.
J-Decker is a cop show parody and can be really, really funny. It's almost pure comedy, though, with a few memorable intense action scenes here and there. Goldran is also almost pure comedy and a very good one, but it has a bit more in the way of plot arcs. Its action is not very memorable, though.
Dagwon was a victim of "Samurai Troopers formula" and as a result is an extremely uneven show. It has some decent episodes, some truly awful ones, and very little overall plot. It's probably the Brave series I like the least, since it feels very phoned-in compared to the others.