For a while I've been thinking about making a post on which Sentai actors and actresses who I think are great singers. In the past decade, many Sentai actors and actresses have sung their own character songs. While others throughout the 80's, 90's, and 2000's have sung theme songs and insert songs. There's plenty of Sentai actors and actresses that have good songs, but these are the ones that I think have the best singing talent (in chronological order). I'm including samples of some songs as well.
Daisuki Shima (Yuusuke)/Red Falcon Liveman
Yuusuke/Red Falcon sung both the opening and ending themes of Liveman. I'm not a big fan of 80's Sentai music, but I think both the opening and ending theme for Liveman are the best among 80's themes. My favorite of the two is the ending theme. Overall I think Shima has a good voice with talent.
Megumi Mori (Megumi)/Blue Dolphin Liveman
Megumi Mori began her entertainment career as a singer before taking the role as Blue Dolphin on Liveman. She sung the insert song "Spark Umi E" on the Liveman soundtrack. That song has a nice rock beat, as you can see on the top video. Megumi also has diversity in her music. The second song I'm showing (Hoshi no Namida/A Star's Tears if my English translation is correct), has a much more relaxed, peaceful tone.
Kenta Satou (Riki)/Red Turbo Turboranger
Kenta Satou (Red Turbo) sung both the opening and ending theme songs for Turboranger, as well as the opening theme for Zyuranger. The openings for both Turboranger and Zyuranger are popular among the Sentai fandom. I personally don't care much for the Turboranger theme song, but the Zyuranger theme song is one of my favorite Sentai themes.
Toshihide Wakamatsu (Gai)/Black Condor Jetman
Toshihide Wakamatsu, who played one of the most popular Sentai characters ever (Gai Yuuki/Black Condor), also sung the Jetman insert song, Honoo no Condor (Flame of a Condor). I think the song is good, but not great.
Nao Nagasawa (Nanami)/Hurricane Blue Hurricaneger
Nagasawa Nao - To you by KHproductions
I had trouble trying to find videos for Nao Nagasawa (Hurricane Blue), but managed to find them. She sung the Hurricaneger insert song "Shinobi Koi" (first video, from 7:03 to 7:28) and also had some mild success in the J-pop industry (her top song reaching #27 on the J-Pop charts). I think Nao has a beautiful singing voice and some diversity in her music (some rock, slower ballads, evens some salsa thrown into a couple of her songs). However, her music is mixed for me, and tends to range from good (like the song in the second video, "To You") to pretty bland.
Shou Tomita (Yukito)/Abare Blue Abaranger
This is the only song that I know of from Shou Tomita (Abare Blue), which is Yukito's character song. However, I think it's a kick ass song. Nice rock beat, and Shou sings it perfectly. IMO it's the best of the character songs by any 2000's Sentai male actor.
Ayumi Kinoshita (Jasmine)/Deka Yellow Dekaranger
Ayumi Kinoshita's song, "Hard Rain," (first video) I think is perhaps the best character song. It has a nice, up-tempo beat. While I don't think Ayumi's is the best singing talent, she's descent and the up tempo beat to her character song suits her well. She also sung the Dekaranger insert song "Girls in Trouble" (second video) with her Dekaranger co-star Mika Kikuchi (Umeko).
Mika Kikuchi (Umeko)/Deka Pink Dekaranger
While Ayumi Kinoshita has possibly the best character song, I think her co-star Mika Kikuchi (Umeko) is the best singing talent among any Sentai actor or actress. She has a beautiful voice that's made for slow melodies. Like other Sentai actors/actresses, she has a character song (Sunao ~ Ima wo Shinjite) (first video), and also sung an insert song on the Magiranger soundtrack (Tenkuukai no Yasuragi/Peace in Heaven) (second video). She's not only good at slower ballads, but at rock songs as well, like the song in the last video, "Chihei no Kanata."
Yumi Sugimito (Miu)/Go-On Silver, Go-Onger
Yumi Sugimoto also has a good singing voice that really shows in her character song "Yume no Tsubasa." She joined her Go-Onger co-stars Rina Aizawa and Nao Oikawa to sing the song "G3 Princess." That song personally I think is ok, but Yumi and Rina both have much better character songs.
Hidenori Tokuyama (Hiroto)/Go-On Gold, Go-Onger
While not an actual character song, Hidenori Tokuyama's song "Miss You" managed to make an appearance in episode 31 (the G3 Princess episode), which I thought was easily the best song in the episode. The song sounds kinda like country, which isn't my type of music, but it's still a good song (the full version of the song is in the video above. I think Hidenori displayed a great singing voice in the song, which makes it easy to listen to.