Well, the "gate of thunder" idea is a japanese one that makes sense to them. in asakusa-tokyo, there is a famous gate called kaminari-mon, the thunder gate. plus, how much sense need a title make? if it helps you, imagine there is a god of thunder who passes through a gate.
silliness aside, GOT is, even to this day, one of the most solid shooters ever. 15 years on, the soundtrack and gameplay are exciting as hell. the level 5 boss music in 5/8 time and the level 6 main stage tunes are just perfect! the difficulty is just right- not too easy but not impossible either though it took me a while to beat it.
generally, as far as the big three 16bit consoles are concerned, the duo had most of the best shooters. the SFC'S macross:scramble valkyrie and starfox are great. the Genny had a few greats (cotton, silpheed, and a few others). i know i'm leaving a few out but GoT outdoes all but one or two SNES/Genny shooters.