A truely innovative game which never caught on due to a somewhat outdated engine
Because it had an actual plot, this was the second FPS (the first being Dark Forces) that I ever had the patience to play from beginning to end. The programmers really did some amazing things with the ol' Doom engine.
For one thing, instead of linear levels the game used a hub system like Hexen where you could go back and forth between several different interconnected areas. Also instead of mission briefings your objectives were relayed to you in-game either by people you talked to or by your everpresent partner "Blackbird" on the radio. This gave the game a smooth transition and seamlessness I hadn't seen since until Half-Life came along.
Also, instead of a dead world populated only by monsters trying to kill you, Strife had various "friendly" areas such as two towns and two rebel bases where you could just wander around and talk to people or buy stuff. Even some of the "action" levels started out friendly and you could even have conversations with the guards (until you started shooting or entered a restricted area, at which point they'd start trying to kill you). Also, there was a great deal of variety to the levels (ranging from occupied town squares to old ruins) instead of the usual endless similar corridors.
When you talked to a major character, you got a close-up screen with comic art and speech. The comic art of the various characters was extremely well drawn, and the speech was pretty good as well. Your partner, Blackbird, also had various funny or oddball things to say over the radio about the various situations you found yourself in.
The action itself was pretty much standard Doom fare, with enemies who weren't too bright but who came at you in ridicuously large numbers. The enemies themselves ranged from the standard gun-toting guards to a variety of cool-looking battle robots. In terms of weaponry there were a few innovations, such as incindery grenades and a flamethrower you could use to sadistically burn your enemies alive, and a crossbow with poison arrows you could use to kill guards without setting off the alarm. There was even an item you could use to teleport friendly rebel soldiers to your location to fight for you (albeit not particularly well).
Also helping to set this game apart were the various set pieces in it. For example, at several points in the game you could sneak past hordes of guards with a fake ID or by pretending to be the janitor. One particularly fun level had you storming an enemy castle, and fighting alongside you was a small army of rebels engaging the enemie's forces in a large scale battle royale which was a real change from the typical one-man-against-the-world FPS scenario. In a similar scenario a single boss-character would show up in the middle of the rebel base and would wind up slaughtering them left and right if you didn't intervene. Finally, towards the ending of the game you were given a choice of two different "paths" which would lead you to two seperate endings. The good ending was your typical save-the-world-get-the-girl scenario, and was pretty tough since you had to go through several extra levels. Despite the grim outcome, I found the bad ending to be most interesting because of the surprise (and boy was it a surprise) identity of the final enemy.
Well, the Doom engine was a bit dated at the time (I believe Quake was just coming out) but the programmers made enough tweaks to it (such as jumping/ducking, more "true life" textures, and a hub-based level system) so that it seemed fresh. I also think it didn't have support for mouse aiming, but when I played the game I hadn't heard of mouse aiming anyway so it didn't really make a difference to me.
Though this probably doesn't apply anymore, when I got the game it really cheesed me that it took a whopping 70 megabytes of hard disk space, and you had to install the full game and couldn't play it from the CD. I know that nowadays you could toss 70 megs out the window and never miss it, but back then I only had 30 megs free on my hard disk (which was all I ever needed for any of the other games I owned) and had to do some seriously weird stuff with my HD to get this game to work. But I think it was worth it. The game also didn't allow you to have multiple save slots for a single game, but a small patch (or creative copy/pasting) fixed this oversight.
My only real complaint was that the very last section of the game (the Order Factory) was pretty much just five levels of repetitive shooting and button-hunting, with none of the interactivity, creativity or atmosphere that made the rest of the game so compelling. However things did pick up when you reached the end of the Factory and got to the endgame.
The Bottom Line
After Half-Life's example, most modern first person shooters contain many of the elements which made this game so interesting. However, for it's time Strife was a very different and very enjoyable FPS experience.