I would say Kamen Rider W is a really great series, it has a few quirks not everyone is going to like, but for the most part it, it feels like one of those series where the crew behind it had an idea of where it was going to end. It's the first time in ages that I watched an episode in the 40s and found myself thinking back to how little elements from earlier episodes are actually coming together to form part of the greater story. Plus, if you end up liking it, there's a lot of extra material to watch, five movies and they're all really good. Well, two of them are short movies, at around 30 minutes each, but what's great about W is that the movies here actually benefit the series. The first movie explains backstory for some of the major elements, the third movie explains more backstory and works as a nice bookend to the series, but we still get two more movies after that and they do a great job at expanding the world. I especially love the Kamen Rider Accel movie because it's the first time we get such a long look at what a Rider's world is like after their series has ended.
Liveman is really great as well, it's an older Sentai that was just recently finished. You can find those subs from a group called Grown Ups in Spandex. (they're also doing Jetman now)
If you're looking for more recent Sentai, Shinkenger might tickle your fancy, it's not my favorite, but I can see why people like it.
Goseiger and Gokaiger are also good shows, admittedly, they've both got pretty huge flaws. Goseiger suffers from inconsistent characterization, a pretty bad cast save for a few members, and core characters that people often felt were a little too sanitized, despite the show's flaws, I'm still a huge fan of it and think it's given us the best Red in who knows how long. Gokaiger sort of throws these "GARBADASS" characters at you, so it's sort of the opposite problem that Goseiger had, though they both suffer from this...inability to really make the villains have any sort of presence throughout the series save for the big episodes. Gokaiger's one of those shows that only gives you a handful of great episodes in the first 30 episodes, basically one of those "It gets better after XX amount of episodes!" shows. The characters are...eh, they can be unlikable at times, but they're certainly not the worst bunch of characters we've had in a while, though I think they suffer from major underdevelopment, but the most recent episodes are sort of changing that. I genuinely feel that 28 is the episode where it becomes a pretty consistently good show, I've only disliked episodes 29 and 45 since then.
Outside of Sentai, Rescue Fire is a really fun show that comes together to have a rather meaningful idea behind its villains. Keitai Sosakan 7 is also the best tokusatsu show that's aired since it came on, though it isn't a transforming hero show, it's more of a mystery show with some funky directing and great characters.