Xevious. It's a perfect arcade port and the exclusive Fardraut Saga has some nice additions to the game, like power ups and different ships for different levels.
Its not exclusive. The same game is on the MSX2.
Sorry, I misspoke. Xevious on the PCE is "Fardraut Densetsu", not "Fardraut Saga". Densetsu is a whole different game than the MSX2 sequel. I always want to call it Saga for some reason. If you don't count Super Xevious, which is really just a tweaked version of the original, the Famicom had the first official sequel with Super Xevious: GAMP no Nazo, MSX2's Fardraut Saga is the third sequel, and Fardraut Densetsu would be the fourth entry on the PCE.
BTW, do you have the first Final Zone on the MSX? There's a video of it on Youtube somewhere, but it's crazy how different it is from the sequel on the PCE/TG.
I'd include Final Zone II on this list. It's not an incredible game, by any stretch, but it's a fun game to sit back and walk through. It's not terribly difficult, so it's a nice relaxing ride. The cheesy dialogue on the TG port is good for a laugh. All in all, it's not a bad way to spend a rainy Saturday afternoon.