It would take a while to link to each of the different sub-series, so here’s a link to the general Koei Wiki instead.
And here’s Koei-Tecmo’s company website.
Now, if I could summarise the Warriors games, it would be “ludicrously violent”.
By that, I don’t mean that the violence is especially graphic or lurid — by the standards of modern video games, it’s downright tame. What I mean is literally that the nature of the violence is itself ludicrous: you press a button, your character slams his sword into the ground, which causes an explosion that sends eight people flying.
Koei describes the gameplay of the Warriors games as centring around “one vs. a thousand” combat. You’re a superhero running wild through crowds of regular dudes and occasionally throwing down with other superheroes. This is, incidentally, completely faithful to the source material.
The flagship series of the Warriors games is Dynasty Warriors, set during China’s Three Kingdoms period of about AD 180-280 (if you want to be entirely accurate, the Three Kingdoms didn’t start until 220; but for now, that’s neither here nor there). The series started in 1997 with the original Dynasty Warriors, which was actually a fighting game, rather than the hack-and-slash action style that the series ultimately settled on.
The most recent entry in the series is Dynasty Warriors 9, which had some interesting ideas and pretty solid character designs marred by rather lacklustre implementation, and a voice actors’ strike that led to a non-union dub that is hilarious for all the wrong reasons — even the several competent performances were pretty egregiously miscast.
The second most notable Warriors series is Samurai Warriors, set during Sengoku period of Japan, focusing specifically on the time between the rise to promience of Oda Nobunaga in in the 1560s and the siege of Osaka in 1615.
By now, there have been four mainline Samurai Warriors games and several spinoffs and expansions, so the series has had time to set itself apart from the earlier Dynasty Warriorses.
The fundamental “you vs. everybody; press a button, punch eight people into orbit” gameplay remains, but there are differences in both the peculiarities of the gameplay — Samurai Warriors characters have sequences of crowd-control attacks not present in Dynasty Wariors — and the storytelling — this period of Japanese history isn’t as neatly divided into the same several large factions as the Three Kingdoms; even focusing on the most prominent regional clans and factions means that each game now has about ten separate story modes.
The two series have crossed over several times now in the Warriors Orochi series, which has a completely new, not-restricted-to-real-world-history story and involves evil gods fighting good gods and Time and Space collapsing in on themselves.
The Orochi games aren’t necessarily better than games in either of the main series, but their biggest strength is that they are allowed to tell a completely novel story, rather than having to relive the same historical events over and over and over — as much as I like the Warriors games (a lot), their being bound by real-world history and refusing to deviate from it is my biggest complaint.
This formula was taken to its logical conclusion in Warriors All-Stars, which actually expanded the roster beyond the Warriors games and created an opportunity to watch the most popular (according to Japanese fan polls) Koei-Tecmo characters beat each other up. It is, however, probably the least well-executed Warriors game.
Also worth noting are the various other Warriors games based on other franchises: there’s a series based on One Piece, there’s one based on Gundam, there’s a couple of Dragon Quest ones. The only ones from these licensed games I’ve actually played at any meaningful length are the Nintendo ones: Hyrule Warriors and Fire Emblem Warriors. Of those two, Hyrule is probably the better one, but Fire Emblem has the advantage of having characters who are capable of speech.
Critics don’t seem to like the Warriors game, decrying them as mindless and repetitive. And, yeah, they kind of are. Recently, though, the games have done a lot more to emphasise the importance of tactics and managing the battlefield, rather than just plowing through the enemy. They’re maybe not for everyone (but is anything), but if they’re the kind of the thing you like, then you probably like the Warriorses a lot.
And even if you hate the gameplay, you’ll probably love the soundtracks.
As a final note, Koei’s Warriors games are most assuredly not to be confused with 1979 movie The Warriors (or the book that inspired it).
… And it occurs to me now that I should probably be recommending more books.