Admittedly, I'm a big Deka fan, and it also took me a while to warm up to Hoji due to his arrogance during the early parts of Dekaranger. I probably have a habit of underrating Hoji, and now I do think he's an ok character. Still, I didn't like it when I read some message boards where Hoji was used to attack Ban, one of my favorite characters in Deka.
Genta, Shinken Gold
I personally never had a problem with Genta like I did with Hoji. Genta is probably underrated in terms of his use and character focus during the series, but in terms of "6th rangers," there's a lot more Sentai 6th rangers that I like better than Genta.
Mako Shinken Pink
I actually do like Mako quite a bit. She is one of my favorite pink rangers in Sentai. In fact, I really don't think Mako as a character is overrated at all. However, I think her actress, Rin Takenashi, is overrated in the looks department. For me, she wouldn't make my top 5 among hottest Sentai girls, although she would still be in the top 10.
When anyone mentions anything about Hurricanger, it is usually about Nanami because of her looks, and if it's not Nanami, it's Shuricanger. These two are among my favorite characters, but I think the Goraijers are often overlook. I think both Ikkou and Isshu are badasses, and they have an interesting story in which they came from a rival ninja school to the Hurricangers and they had a father who didn't give a shit about there lives, as long as "that" was born. It took them a long time to get over it and to warm up to the Hurricangers, but I think both of them, especially Ikkou, are interesting characters.
I realize that Umeko is a bit of a "your mileage may vary" type of character. Some criticize her for being under developed or being "meaningless" to the show. While she may be a little bit under developed, I don't think she was meaningless. Personally, I liked her cute, funny, and bubbly personality. In fact, I'm a bit of a sucker for girls with bubbly, girly-girl personalities, which is why the next two characters also make my list. I also liked it every time she was doubted by the other Deka's that she would prove them wrong :P
As mentioned above, I'm a bit of a sucker for girls with cute, bubbly personalities, and Natsuki is one of them. True, she's not really much of a fighter, she's a bonehead, and she's childish, but she's childish in a cute way. I also think she has one of the most interesting background stories out of any Sentai character. She was a princess of the extinct Lemuria civilization, and put to sleep in suspended animation for 100,000 years. She aged 1 year for every 5,000 years she was a sleep. When she woke up, she had amnesia and no memory about her civilization. I also think the two-parter in which her true identity was revealed was epic, among the best episodes during Boukenger.
Saki, Go-On Yellow
Another character with a cute, sweet, bubbly personality I like. Rather it's because people don't like Go-Onger or the people that do like Go-Onger for either the Go-On Wings or for the good comedy, I think Saki gets overlook on both sides. For me, she's one of the main reasons why I like Go-Onger. She's always cheerful, and always has a smile on her face. Interestingly, she has a rather heartwarming story about why she is always smiling and encouraging others to smile.
Kaoru, Shinken Red
I know Kaoru was present in Shinkenger for only 6 episodes and was heavily underdeveloped, but being the first female red ranger in Sentai's history was historic. Some criticize her for being a spoiled brat, which I disagree with. I think a lot of people, mostly Takeru fanboys, get the wrong impression about her when they meet her annoying retainer, Tanba. She is actually quite a descent character and was smart enough to know what to do with the situation she inherited, and tried to lead the Shinkengers and fulfill her duty while recognizing they had a better bond with Takeru.