I would stay away from 555 because, well, it kinda sucks. The first 12 episodes or so are great, but it really goes downhill once Kusaka pops in. I would recommend Kamen Rider Agito, it's one of the most complete tokusatsu shows out there. It's got an amazing story that ties in so well to all of the characters, not to mention it's also got a fairly decent cast. It may not be as "dark" as some shows, but I find those to be overrated.
I don't know why people have such a love affair with Garo though. It's a decent show, but not much else. The action sequences weren't even that good, yeah the suits were amazing, but it doesn't matter when it stifles any real action and we're left with some pretty bad CG...which I guess isn't too bad by Japanese standards, but I guess I'm just too used to Western stuff to have found it all that interesting. That's just the aesthetic side, the characters were pretty dull, aside from the Kouga and Kaori relationship at first, but that goes to heck pretty fast. Everyone else seemed pretty predictable and stale.