It's not as good as people say it is. It's not bad, but I don't think it deserves all the "OmGz! Garo is da bestisis in da hol wide wurld!" that gets thrown around all the time. Yeah, it's a very dark tokusatsu, but that kind of gets worn out after a while and sometimes it feels like it's just relying on the fact that it's aimed at an older crowd to get by. It is fairly good once the plot hits, but even then there are times when it gets kind of stale. Kouga and Kouru are pretty fun to watch, but I couldn't stand Rei most of the time. Tsubuasa in the specials was an awesome character though. Now I would love to see a series with him as the lead.
As for other tokusatsu series, the number one series I can recommend is Kamen Rider Hibiki, without a doubt my favorite show out there. And Kamen Rider Agito as well, another masterpiece in tokusatsu. Beyond that I would say anything from Ultraman Nexus to Mebius, those are easily some of the best Ultra shows out there. Also, check out Ryukendo, it's a comedy heavy series, but it was a blast to watch and great in its serious moments.
If you're looking for something a little bit older, Jetman, Changeman, Kamen Rider X and Ultraman Leo are great too.