Sorry, my reviews aren't up yet. Here's the short version:
Gatchaman: It's great, get it.
Gatchaman II: It's also great, get it.
Gatchaman Fighter: Only the last ten episodes are worth anything.
BOTP: Unless you loved it as a kid, avoid it.
G-Force: Terrible names, terrible voice acting, terrible music, slightly decent scripts. Depends on what's more important to you: good story or good acting?
Eagle Riders: The first 13 episodes were not too bad. I hear horror stories about the rest of it, though.
Gatchaman OAV: Slick, modern, totally revamped character design (that except for Berg Katse is UGLY UGLY UGLY), sucky music and no characterization worth speaking of. If you love what's new or you lust after Berg Katse, get this. Otherwise, avoid.
Gatchaman OAV sub: If you must get the Gatch OAV in English, this is the one to get.
Gatch OAV dub: Avoid unless you hate subtitles or really can't afford the $10 price difference per OAV between a sub and a dub.