Hello CkRtech. Welcome to the party.
Out of the lot you scored I'm familiar with
-Populous The Promised Lands
What can I say it's Populous
It's as fun as it always is and played the same as it did on every other system. Not a mega must own but a fun game that's cool to have.
-Neo Metal Fantasy
This one I got because Black Tiger proclaimed it's greatness and then was kind enough to provide a walk through of the game. Reminded me of Phantasy Star fun game and seemingly under rated for some reason. Very playable in that old school way.
You say your an RPG guy. If you don't mind stumbling around Japanese RPGs aided by a walk through there's quite a few good ones on the PC-E. The entire Far East of Eden series is easy to find for cheap prices (really I think I got all three for around $25) and has walk through online and is mega fun once you get into it. Then there's stuff like Legend of Xanadu II which while somewhat harder to find is an amazing game to look upon and play. Probably a bunch of other good stuff I'm missing but that's off the top of my head.
For the English/Japanese RPG stuff (be prepared to be driven insane by price comparison):
-Neutopia I/II
I beat the Japanese versions of both of these games. They also tend to go cheap ($8-10) with the American versions being overpriced and part II entering the realm of stupidly overpriced on Ebay. If you can find them in English and not break your bank account getting them by all means do so
But the Japanese versions are playable on their own and part 1 is damn near idiot proof. It plays exactly like Legend of Zelda complete with bombs, healing potions and so on. If you've played Zelda you can play this. Heck even the plot's the same...
-Y's 1&2
Get this in English if you can. I've seen Ebay drive up this game but if your calm and lucky you can get an English copy without selling a kidney. I think I got mine for $20 which for a game of this quality is worth it. I also own the Japanese version (I'm an Ys geek) still playable but the game has a good plot and the American version is well translated. I can't over rate this game enough.
-YsIII
The Zelda II of the Ys series. I like it but several folk wish for it's death. Not a horrific game but not the best in the series either. Kinda short, has scrolling issues, weird difficulty curve... Price comparison USA $50+ Japanese version $7-$10. But yeah that's normal as you can see. When it comes to this game I play the Japanese version with a script copy laying near by. The American version is not that well translated imo and the voice acting makes me prey for the sweet embrace of the abyss.
-YsIV
BUY. NOW. There's only a Japanese version but there was a fan translation so make an iso of your game disk and patch the iso and you have a lovely copy of Ys IV in English you can now burn on a blank CD. This game is awesome. Fantastic animation a pretty good plot and amazingly playable. Yeah it's non canon but so what it's Ys shinning hour imo. Gaming has rarely been this fun for me (continues to over hype Ys 4)
-Cosmic Fantasy 2
Another you really should get it in English games. Ebay hasn't driven this one to insane prices yet...last time I looked anyway. Very fun little RPG. A lot of people like it I dug it myself. Part one was only released in Japan but is easy to play due it one being short, two mostly linear and three having a walk through online. CF2 is a much better game.
-Might and Magic III
Never seem then English version go for a price that wasn't insane. Apparently this game is rare.
I don't own a copy of it in either language. One of those games I'd imagine you'd HAVE to play in a language you understand due to it being a big wall of text...
-Dungeon Master: Theron's Quest
I own it but never played it much I need to get on that...
-Dungeon Explorer I/II
Own the Japanese version of part 1 not much text to speak of and playable in any language imo. It's Gauntlet's best possible big cousin. Part II is part one but prettier, more anime cut scenes, and more levels, awesome game. For some reason over priced on eBay way past it's real market value. Get it from here:
http://www.japangamestock.com/ these folks eat my wallet...
-Dragon Slayer
I own the US copy of this one. Another one of those that ranges from fairly priced to utterly batshit on Ebay (see Ys same deal as that game). It's a wonderfully old school RPG that if you play it right is no cake walk but shouldn't destroy you. Be prepared to bash for loot like any good old RPG. Fantastic cut scenes and a great opening. The American version is sadly plagued by some legendary awful voice acting. Luckily there isn't much of it. The awful voice acting will either make your ears bleed or amuse you endlessly.
-Dynastic Hero
Wonderboy~! side scrolling action RPG. Same drill as before American version $ = THIS IS MADNESS~! Japanese version goes for $9 welcome to the wonderful world of collecting games for this thing
Would be easier in English but the game isn't that dialogue heavy for what it is. I do recall needing a walk through for some parts however.
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-Yes you should buy Gunhed wait never mind seems you own it already
and Lords of Thunder and Salamander (side shooter) and also Super Star Soldier. Can't forget R Type either if you like a side shooter format...seriously if you not a fan of shooters this system will make you one on the sole basis that it has so many good shooters for it. You'll never tire of shoot em ups as long as you have a PC-E.
-Valis is interesting. I'd say if your going to get any of em III is the best. It has the most playablity out of the whole series aside from the normal great cut scenes and good look of the series. II as said has some rocking music but it's by the numbers.
For other side scrollers can't go wrong with Legendary Axe I and II, Adventure Island (Dragon's Curse in the US), Takahashi Meijin no Shin Boken Jima (New Adventure Island in the US) and ahh what else...oh Ninja Gaiden has a great version for the PC-E and thanks to a code on the title screen you can play it in English and the translation is pretty good to be honest.
And no collection is complete without the PC Genjin/Bonk games.