Got Syder Arcade. Its good, but I never really felt the pull of things like R Type and all those as hard as I did from danmaku titles so it didn't keep my attention even though it was highly polished. I'd say if you like the older shmups this would be a fantastic evolution in both style and shot patterns you would enjoy.
Kromaia I straight up passed on due to the color palette coming off as an obstruction to the action instead of a compliment. Too easy for me to lose myself in it. If you liked Forsaken though you'd probably enjoy this a lot. Just don't play it if you're prone to seizures or headaches from flashy screens because it looks like it could cause eye strain heavily with the way its palette is setup.
Raiden 4 Overkill is fantastic. Ships all feel super fast and powerful, shot types all feel great, dodging is super tight, soundtrack, modes...its just superb. By far the best of the bunch. If you have to choose one choose this one unless you have some severe nostalgia for Forsaken or older style shmups eating at you.
Again though...I'm more a Danmaku guy. I adore Cave titles, Treasure, and I tend to enjoy things like Neogeo shmups such as Ironclad/Blazing Star if I go more classic. Take that for what it is because I know it means my opinions are weighted towards those tastes.
Would any Gradius, R Type, Darius style old school fans like to weigh in on these? I'd like them to get a second opinion from folks geared to the other side of the shmup spectrum too and not just hear me lust after the bullethell title the most like always.