TL;DR
A throwback to my childhood that's still enjoyable today, although it does have some hiccups due to its age.
Story
A gang of bandits have been raiding trains and no one dares go after them. Bounty hunter John Cooper is only one interested in apprehending the leader of the train robbers and he sets out to assemble a team for the job. Add some misdirection, framing for a murder, robbing the robbers and so on for some cliche drama and you'll have a serviceable plot to hold the game together. The story isn't really anything to write home about and the game doesn't overexert itself with more than just the bare minimum of a couple of so-so cutscenes in-between levels for some plot, but it's enough to have an overarching plot at least. You're probably here for some good ol' western shootouts rather than some groundbreaking-level plot anyway. Honestly, this was one of my favourite childhood games and I didn't even understand what the story was back then, since I was playing a version of the game that was in Russian... not one iota of which I could actually comprehend back then.
Gameplay
Desperados is an isometric real-time tactical game, where you control a team of bounty hunters against a map full of bandidos. The idea is that while you can just shoot everyone you see to get your mission objectives over with, you are by far outnumbered by the baddies and your guns overheat with use, so you have to be smart with how you eliminate the henchmen in-between you and your mission objectives. You can go with a stealthy approach and kill off enemies one-by-one (or in small groups) without alerting the entire map to your presence, but you can just as well go loud if you find a way to limit how many of them can get to you at a time. For example, you could place a snake at the top of a ladder so that the bandidos die from venomous bites each time they clamber up. Or you could draw them to an area with some noise and throw a bottle of sleeping gas at them. Or bait them into climbing to the second floor of a building and knifing/shooting them each time they come through the door. There's plenty of ways to go through each level, both for those who love pure stealth, and those who just want to go on a murder rampage.
Each character is equipped with an arsenal of five weapons/items/actions. The first slot of every character is taken up by a firearm (except for one having a blowpipe) - each different in its ammo count, firing speed, range, damage output and so on - but all the other slots are unique. One character can throw a knife for a silent kill, another can draw attention with her thick thighs and then kick them in the balls when the poor fools get close enough, while a different character can solve a lot of problems with a good ol' rock throw to the face (turns out the humble rock is the sure-fire method to put people out of commission with the biggest range in the game). On the one hand, all of the characters are unique in what they can do; on the other hand, the characters can be horribly overspecialised for certain tasks. Only one specific character can saddle a horse (and he's the only character who can carry bodies for half of the game), only one other character can tie up unconscious NPCs so they don't get up again, you need another character to patch up injuries or unlock doors and so on.
The game is rather clunky, as could be expected from its age. The controls could be more intuitive, and you can't run-and-shoot or do other concurrent actions with the same character. There is a feature that allows setting up actions for multiple characters to carry out at the same time, which is a nice way to set up a team strat for a specific situation, but it does have its hiccups... since closing in on a target and using an item are considered two separate actions, so you have to manually order the character to close in and then use this feature to quickly trigger the character's ability.
Level Design
There are 25 levels in this game. Most take place at new locations, through a couple of levels reuse the setting of old levels. Some levels take place during the night, some in rainy weather, but weather conditions don't change over time. The levels are all 2D with no camera rotation, which can make it horribly hard to notice enemies hiding behind corners, since most of the levels have tons of buildings scattered about.
Overview
The Good
+Holds up well for a 2001 game;
+Most levels allow both stealth and brute force tactics;
+Nostalgia;
+Quite a lot of different levels;
+Cheap
The Neutral
*Enemies are frequently unpredictable
*Soundtrack
The Bad
-A bit clunky;
-No camera rotation;
-Enemies deal far too much damage from long distance compared to you
-A lot of character actions are useless or highly situational;
-Characters are a bit overspecialised for certain actions (e.g. only one character can saddle a horse or tie up a guy)
-Tutorials don't explain some basic features;
-Transitions between levels are lacklustre;
-Final character gets introduced so late into the game that you barely have time to use her;