This was actually the first of the "Musou" strategy-action games, as the first Dynasty Warriors was a one-on-one fighter on the PS1 in the style of Soul Edge. This game sets the familiar pattern that the series is still following -- put down the Yellow Turban Rebellion, the beast Lu Bu must die today, pick one of the Three Kingdoms to fight as, all to the tune of butt rock -- but naturally with less features than later entries, and unfortunately also with many more missteps that wouldn't be ironed out until later.
Fewer playable characters here than anywhere else in the series, with the leaders of each force held out of Musou mode (though they appear on the battlefield under computer control and can be played in "Free Mode"). Fewer maps too, with only eight in total. There are cutscenes in this one, but no voice acting on the battlefield.
The game is still solid on the whole, and you can't really fault it just for not being as good as its sequels. You can fault it for the wicked slowdown when too many guys are on the screen, however (and particularly when two or more horses are around). You can also fault it for having a particularly obnoxious camera, even by series standards.
You can also fault it for some gameplay hinks that wouldn't come back in later entries. All the enemy commanders, even down to the lowly Gate Commanders, seem to have an infinite supply of healing items and buffs stuffed down their pants and use them automatically when they get up from a knockdown. I get that it was a primitive attempt to keep people from rushing ahead of the action and soloing them, but even when you have them surrounded it takes an insane amount of time to wear them down sometimes. On a related subject, gates don't switch hands in this one -- each side just starts with a certain amount of them, and when the commander is killed its closed off for good to both sides.
... And we're fighting *against* them?
Ally AI also just seems markedly dumber and more passive/helpless than in later entries. While all the games require you to charge around the battlefield on a horsie personally intervening in different skirmishes to some degree, literally everyone past the first map always seems to constantly be losing if you're not involved, even if you're keeping morale high by winning your own battles. The amount of running back and forth in some maps to keep battles from going sour is insane.
The game isn't bad, but was better when the premise was totally new and the sheer amount of characters on-screen was technically impressive in spite of the slowdown. With better options on the PS2 let alone newer systems, however, there's little reason to revisit this one. Even the butt rock isn't as good as Dynasty Warriors 4 :(