The X68000 rendition of R-Type is very interesting to observe in action. It is not quite arcade-exact, and so it's not as close to the arcade as the PS1 R-Types version is. The PS1 port itself is not 100% arcade-exact because of the difference in screen resolution: PS1: 320x220 pixels (or something very close to that) arcade: 384x256 which is significantly higher resolution, but otherwise the PS1 ver. is basicly the arcade game, a carefully rebuilt port for the PS1 hardware.
X68K R-Type is better than the PCE/TG-16 & PCE SCD versions in some areas:
*graphic detail
*parallax scrolling
*sound & music (debatable)
*perhaps color palette as well but it's hard to tell
yet worse in other ways:
*scrolling speed/smoothless was definitely slower/chopper than PCE/TG-16
*animation of certain objects like missiles was really slow
*music is overall better on PCE, even if technically the X68K has advantage with FM Synth.
Concidering that X68K R-Type was made in 1989, while the PCE version was made in 1988, and also concidering the vast hardware differences between the X68K and PCE, there's no excuse for the X68K version not living upto and surpassing the PCE version in every single area.
Overall X68K R-Type is a faithful rendition of the arcade for a home computer system that blows the ever-living snot out of the weak AtariST-quality Amiga version, is lightyears ahead of it, and every other home computer rendition released in the late 80s/early 90s.
If the Amiga or any other home computer had been given a version of R-Type precisely identical to the X68K port, it would've been worth its weight in gold. Such a thing would've been hailed as the arcade coin-op machine playing on your home computer.

However, for the X68K, and by its standards, this rendition is actually sub-par. It's not the usual X68K quality of incredibly near an arcade game, like say, X68K Salamander or Fantasy Zone, ports that are so close its hard to tell.