Jetman's theme song is pretty cool. The song fits well with both the intro and the fighting songs.
I like Zyuranger's opening theme song, a lot better than its ending theme. It's not quite as cool as Go Go Power Rangers or some of Sentai's other theme songs, but it's still a pretty descent song.
Megaranger's opening theme is by far my favorite 90's Sentai theme song. The song starts out kinda slow but it still has a fun beat.
I like the Timeranger theme song a whole lot better than the Power Rangers Time Force theme song. It has a strong beat, it's fast pace, and goes quite well with the intro. It's a pretty intense song for a pretty intense season.
Dekaranger's opening theme is awesome. It's by Psychic Lover, and just about every song by Psychic Lover is awesome. By far my favorite Sentai theme song and I often catch myself singing along with it. It also surpasses all of my favorite Power Rangers theme songs.
The Gekiranger theme song is also pretty awesome. Like Deka's theme, I often find myself singing along to it and it fits the intro quite well. The intro is also pretty awesome with all the martial arts action, except for some parts in the early part of the intro where the foot soldiers look more like they're dancing instead of fighting.
Go-Onger's theme song is also quite catchy and fun. Much like the series is. Not quite as awesome as the Dekaranger, Gekiranger, or the Shinkenger theme song, but still fits the series quite well.
Shinkenger's theme song is another totally awesome song. It's a collaboration between Psychic Lover and Project R. Catchy and energetic. It's my second favorite Sentai theme behind Dekaranger's. The intro is pretty cool as well.