Gekirindan is a very good time and I would think much more of it if it weren't for one big flaw - it can be very easy.
On the pro vs. con scale, that's not the worst con to have, and in fact, I can't really think of another con the game has. So, if you are not an awesome player (I'm certainly not), or if you want some mindless blasting action for a while (it gets harder later), there's a lot to like about Gekirindan.
You choose from several ships to start and you are off and running. It is a time travel theme and the stages have drastically diff graphics and themes based on which era of time you are in. You are chasing some boss-bastard around the universe and time and in the middle of battles with him a vortex will open and he will disappear (coward).
You have two buttons to go along with the joystick. The buttons are (surprise!) fire and bomb. You can also achieve rapid fire by holding the fire button down... there seems to be no penalty for doing this and no limit to using it - part of what makes the game seem a little too easy.
The other part of what makes the game easy is the plentiful and powerful power-ups. Between collecting this crud and the rapid fire, you quickly start blasting things without much effort.
Luckily, when you die, you start back from scratch and without all that firepower, the game is much more difficult (as it is in subsequent levels anyway).
Graphics add a lot of punch to the fun in this game. The bombs have really cool animations (diff for each ship). There are bonus emblems (eagles and crap) to collect for points and they also look cool. The backgrounds often have floating spaceships and space stations that seem to be rotating, some in glorious quasi-3D. The sheer variety in the snaps I posted here shows you how much stuff is going on in the game.
There's a ton of action and it's great to look at and blast away at, just don't expect much challenge and you'll enjoy the Gekster.