My personal favorite is Nemesis SCC
I love the game, reminds me very much of the original Nemesis arcade game 
Not forgetting that Nemesis was the first MegaROM game Konami released. I remember a friend in 1990 laughing at me because I said I was a MSX user, some one else in the same group asked me "Have you got Nemesis?" I answered quite proudly that I had Nemesis 1,2,3 for the MSX, he was so jealous!!
Parodius is nice too, and considering that it is just a parody, it has a quite high difficulty level!
Konami made the MSX games a lot harder to finish in comparison to the games they released for other systems.
I remember playing Parodius in the Game Boy back in the early nineties and it was sooooooooooooo easy. When I bought it I expected the same difficulty as in Salamander or Nemesis 2 for MSX. In Parodius for GB you can even select the difficulty level 
There's only one game that can beat the whole Nemesis saga+Space Mambow:
Phantis by Dinamic 
mmm
what are these Yu-Gi-Uh! Trading Cards thing Frmo KONAMI
GRADIUS (Light)
[MACHINE]
A high perormance jet fighter with power capsules for variable attack capabilities
1st Edition PSV-089
ATK/1200 DEF/800
10992251 Copyright 1996 Kazuki Takahashi
Yu-Gi-Oh! (not Uh) trading cards from konami 
What do you mean 'what are these'?! You've answered your own question!
Yep... and James Burton is the hero-pilot and Dr. Venom the evil alien, brilliant brainstorming from Konami
...the names aren't important, Nemesis 2 is the best.
sexy parodius is the best!!!
hehehe
hahaha