Story- Typical good guys(Gradians) v.s evil colony/hive mind type aliens(Bacterians). Some decent twists here and there, but nothing noteworthy. This series is based off the Gradius and Salamander game series. Which are oldschool 80's schoot em' ups.
Animation- Actually pretty decent. Lots of great actions scenes with many ships, lasers and explosions. and the boss battles were particularly well animated. The characters looked pretty standard for 80's animes though and the ship designs were pretty boring too. The bosses looked badass though, especially the last one.
Sound-The only memorable themes are played during the action scenes and are very likely taken from the games that this series is based off. Either way it gets you hyped for the actions scenes.
Characters- Eddie, British Prince and Paula are the only memorable characters in these OVAs and even though they might be a little stereotypical they atleast play their roles well. Everyone else seems just like canon fodder, but atleast they're there.
Overal- Honestly I wouldn't suggest this unless your already a fan of the games this was based on. The first OVA in particular was quite a bore to watch it gets better in the 2nd and 3rd OVA but its nothing you should go out of your way to see.