None of those are overrated. Pulstar is high level rote memorization and very well made for the time it was released. I imagine it would bore most Wii-era gamers to tears. It isn't gorgeous and it isn't easy if you only try it half a dozen times. You have to be a fan of early 90's horizontal shooters and if you are; this is one of the better ones.
Battle Garegga is listed Top 5 all-time on every respectable poll i've seen and ranked that high - it still isn't over-rated. The medal chaining is an easy mechanic but very difficult; particularly stage 3 and beyond. Use of rank is as well done here as in any game. There are many ship selections and the differences aren't just color like in some games. The increase of speed, power, and bomb from one ship to the other is instantly noticeable and finding one to match your playstyle is part of the charm and genius of this game. It plays fast and hard, but fair.
Soukyugurentai i'm not a fan of - i've never been very good at lock-on shooter mechanics, but of games that use that mechanic - this is the best i've played. The ship selection is standard far slow/power / average / fast/weak, but the music in this game is outstanding as are the explosion effects and boss fights.
Now for over-rated shmups...Bullet Soul bored me to tears and was highly praised. It played with a lot of noise and bullets, but stages were too long, too repetitive, and allowed you to sit in the pocket too comfortably. It might be deeper than it appears, but I was too bored to find out.