Every single time I try to play System Shock 2 I keep telling myself that I should be playing System Shock 1. I end up turning it off and playing neither. I think something died inside me.
It's mostly what I've thought while playing SS2 as well. It wasn't a bad game, but... that's it? That's what everyone is talking about? I played SS2 shortly after finishing SS1, and it was like I jumped straight into a pool of decline. No matter how I looked at it, it seemed like massive casualization – gone was the intricate level design, gone were many of the actions you could take, even the difficulty seemed very significantly lower... SS2 had better graphics, obviously, and better UI (which was pretty shit in SS1 truth to be told), but those are minor things compared to what was lost.
I quite like SS1, but this feels pretty reductive to me. SS2's levels are certainly less complex and mazelike than the first game's, but they're also populated with thoughtful encounters against more challenging and dynamic enemies. With a few notable exceptions (e.g. Cyborg Assassin, Autobomb) most of SS1's enemy roster just shuffles in place and hitscans the player. By contrast, SS2's hybrids will aggressively chase after you, monkeys and midwives will pin you down with energy projectiles and fend you off in melee attacks up close, Cyborg Assassins will run away to bait you into a spot where they can more effectively pelt you with shurikens, protocol droids fill the autobomb role with kamikaze rushes, the droids are massive tanks that box you into hallways and spam dangerous energy bolts, and we have
actual turrets as static defenses instead of enemies that just behave like them. Enemies come in fixed placements, scripted ambushes, and dynamic respawn roaming so there's always a threat around the corner and you can easily get caught off guard while managing your inventory or hacking security. SS1 had all of this too, but aside from a few memorable encounters (like the mutant elevator ambush on Level 2, SHODAN's Death Machine on Level R, the Nice Jump ambush on Level 4, the Cyborg Assassins tucked away in sneaky places on Level 8), most of the combat runs together in my mind even after playing on the hardest difficulty settings. SS2 is filled with clever enemy setups, like the Maintenance Droid charging the Medsci hallway unexpectedly after you get the access keycode from Grassi, or the staggered bursting of Protocol Droids out of shipping crates in the Cargo Bays, or the dozen hybrid/midwife/assassin/spider ambushes I can think of throughout the game, or something as simple as a worm egg placed underneath a camera in Hydroponics A so you get trapped in a corner by the worm while trying to avoid the camera's sightlines. A lot of these are possible only because the level design has chokepoints that expect the player to enter and leave through a particular route.
That's all without getting into SS2's heightened focus on resource management, inventory selection, and character upgrades which result in vastly different approaches to each combat scenario depending on your other choices. SS1 has a sizeable weapon roster and some light inventory management on its own, but ammo and healing items are comparatively plentiful and most players will be relying on the same selection of gear as one another depending on their progression through the game. I'm also not sure what more you're looking for in the player's actions? The Von Braun lacks Citadel's secret wall panels and cyberspace is (happily) a thing of the past, but SS2 has plenty of interactivity beyond combat. Cameras are now tied to meaningful security systems, there's a bunch more to hack and repair than SS1 had with its grid and wire puzzles, there are alien artifacts to research with chemicals, and there's comparable platforming here and there. We're lacking SS1's roller skates and jet boots, but the suite of 35 psionic disciplines more than makes up for it. SS1's rearview mirror, headlamp, and night vision are all less interesting to me than SS2's implants, and I prefer SS2's armor system to the energy shield and envirosuit. I'll grant that SS1 had a more interesting patch system, as well as better use of darkness as a gameplay element. More initiative was also expected from the player in solving the progression riddles by finding audio logs and piecing together clues in SS1, while SS2 gives the player explicit directives, at least early on. But in terms of overall difficulty, were it not for some unfortunate discrepancies in balance that allow for significant metagaming I'd say SS2 on the hardest difficulty is quite a bit tougher than SS1 on its hardest settings, even factoring in the latter's 7 hour time limit.
What's funny is I actually think UI and graphics were strengths of SS1 compared to its sequel. Manually managing your interface in the heat of combat was often a greater source of tension than the enemy design itself in SS1 and led to some interesting simulated interactions with throwing grenades and reloading your guns, and I found the vibrant cyberpunk aesthetic of Citadel Station to be more fleshed out and unique than the rather barren hallways of the Von Braun, though the latter certainly establishes a menacing atmosphere of its own. Both games have their strong points, so it confuses me when people describe SS2 as this massively casualized product of decline when the likes of Bioshock exist.