I've been playing the Gunvolt series and I coincidentally happened to start doing so just in time to jump on the third game right after. They're 2D platformers with an emphasis on score-attack-style gameplay where you play as a few different characters with different styles through the series. The main gimmick is that an idol will sing for you when you accrue a certain amount of score.
I'm not actually a big fan of these games overall. Luminous Avenger iX (just the first one, the second is awful) is great fun because the character you play as (Copen), while fairly basic, is fundamentally enjoyable to play: you ping-pong around the level and off of enemies, each "air dash" has limited range but the range is recovered by an angled bounce off of a surface, and each time you bounce off a surface you regain one unit of the resource that is used per air dash. You find the optimal route to bounce through the level without landing, it's a blast.
Through most of the first two games you play as Gunvolt and he sucks. His whole mechanic is that he has a gun that can put up to three tags out overall on to enemies, and then you hold a button to do damage that is proportionate to the number of tags you place. Getting simultaneous kills is how you score. Some enemies take more damage, so you'll perhaps put two tags on one and one tag on another to balance it out. That's basically it. There's a broken skill system that they neutered in the second game. The level design sucks. There's even a levelling and crafting system, and some of the equipment you craft is essential to gaining a high rank.
Gunvolt 3 is like a smart person took the ideas of the previous games and expanded on them. You play as a new character called Kirin, a ninja with a sword and sealing talismans. You tag enemies with talismans (basically like Gunvolt's gun) and you can do a homing dash attack that kills or damages any tagged enemies and teleports you across them sequentially; some enemies require just one tag and big enemies require more. You have one air jump but each dash attack resets that. The challenges of the game are to stay aerial (like Copen) and multi-kill enemies (like Gunvolt) at the same time. You also have a sword combo and a variety of special moves including, usefully, an upward sword attack that can be used in the air and which elevates you. You can also switch to playing as Gunvolt, who is more powerful in terms of damage output and has infinite air jumps, can also do the tag-homing-dash-attack with the same multi-kill scoring mechanic from prior games, but playing as him also uses a limited resource that you build by playing as Kirin. Oh yeah, and you can shoot at 45-degree angles, something that wasn't possible before. It's really thrilling to play and my favourite game of the year so far.