in japan the genesis version cost 3000 euros even in used. it's logic to revamp the game and resell it for gba so other people can play this game. It was average on genesis and i am really surprised to see it on gba. Anyway if you merged the genesis and snes collection into the gba then you obtain the best 16 bits handheld ever made, which is quite disapointing when you know that the gba can do far better things (iridion 2).
Ok thunderforce 4 request again...
edit : i have tested the game and here are the difference/similitude :
the boss have all changed, neither best nor bad than the original
the graphics are far better than the original but there is a [tramage] (sorry) not in the original so it's a bad and good point at the same time
the music is the same as on the genesis but is less good in term of quality (they weren't fantastic on genesis but better than this)
the game slows at the same place in the mine as the genesis version, meaning that the slow down is volunteer so you can avoid the rocks that falls on you.
the mega bomb is different
the lighting effect in the mine (stage 2) has disappeared (why ? it was an originality of the genesis version)
the game is quicker than the original but a lot of frames were removed to obtain the result, the game is still fun but not as smooth as the original
the sound effects are really cool
the beams and power up are different from the genesis version (orange in the genesis, blue on gba)
i think that this game is more fun and attractive that r type on gba and i ranked this game as 3 behind iridion 1 (second place) and iridion 2 (best of all on gba).
it was a good port, remasterized correctly but it's a port again, again, time and again.