This is a sequel to the game Uncharted Waters, though I haven't played the original, so I won't be able to say how it compares to it. Furthermore, while I know this game is pretty much completely unheard of in the UK, I don't know how well known it is in North America or other areas. It feels like its English release would have been pretty niche at the time, though, so I think we're safe. Before I gave it a try a few months ago, I had no idea what it was about or what kind of game it was, other than it being one of those 16-bit Koei games that are about real historical things and have many screens full of numbers to look at.
What I got, though, was a pleasant surprise! It is, amazingly, a pretty big open world RPG, with the world in question being the actual Earth, as it was in the sixteenth century. Obviously, it's not 100% accurate, but if you have at least a little bit of geographical knowledge, you'll be able to put some of it to use while playing this game. It really is incredibly open, too: you can be an explorer, a trader, a conquerer, a pirate, probably some other jobs, too. While I've played it, I've always been going the explorer route, with a little bit of trading on the side. (My tip is to go to Lisbon and get the local rich guy to be your patron. He'll pay you handsomely for every discovery you make!)
So as an explorer, I've spent a lot of my playtime sail near coastlines, waiting to find new ports (where I can resupply food and water, stock up of stuff that might be sold for profit elsewhere, and when necessary, recruit some sailors), or villages. Villages don't have the facilities of ports, but they are where you make discoveries. Every village has a discovery to make, though at some of them, you'll have to give food to the locals a few times before you find them. And the discoveries will be all kinds of stuff: monuments, treasures, plants and animals, foods, and so on. Taking the explorer route is slow and repetitive, but there's still something really compelling about sailing around, finding new things, and really hoping you'll find a new port as your supplies run low in the middle of nowhere.
Unfortunately, due to the way I've been playing the game, I can't really talk about how combat works, since I've managed to avoid it entirely. In my defence, engaging in combat in other Koei games of this era has always been unbearably tedious and also incredibly difficult. Trading works as you might expect: you buy some local specialty in one port, then sail to a port far, far away, and sell it all for a big profit. The problem is that you only have a limited amount of cargo space, and goods take up space that could be used by food and water, allowing you to safely sail further without stopping. THat same goes for cannons, too. Supply management has its own balance to maintain, too: the more sailors on board your ship, the faster you sail, and the easier a time you'll have in general. But also, more sailors mean that you'll burn through your supplies, too. Plus, you have to pay them a monthly wage, which will be hard to afford in the ealry part of the game, before you've established a decent income source.
New Horizons is a game that I've really enjoyed, a lot more than I expected to, even. It's really impressive that such a big and open game existed on consoles in the early nineties, too! The real world setting is something upon which I'm a little conflicted, though: as I said above, it makes things a little easier if you have some geographical knowledge, but also, I think it might have been a little more interesting to have the game set in a fictional world, so that the things you discover could also be fictional, and by extension, more of a surprise. But anyway, I definitely recommend giving this game a try. Especially if you're able to emulate it on a handheld!