For my money, Blood remains the undisputed king of Build Engine FPS games. Ion Fury has some strong points but has too many mediocre (or worse) qualities to really rise to meet the new wave of retro FPS games. Ion Fury has pretty good level design. I'm rarely lost looking for a key or switch and most of the levels do the Romero thing of looping you back to the main path and putting new enemies in your way when you need to backtrack. While the level layouts are generally well done, you do spend a lot of time in industrial tunnels/sewers/cramped spaces that get a bit repetitive. The outdoor and city areas are the most fun to play in and they disappear from the game about 1/2 way through save for a smaller outdoor section of the mansion level. The music is solid as well but I don't think, after 10 or so hours of play, I'd be able to hum a melody or correctly identify any of the tracks removed from the game. The weapons are mostly serviceable. None of them are terrible to use but none of them jump out as a favorite. If I were to be charitable, I'd say they're evenly balanced. More critically: none of them are all that fun. I really wish the game had at least one big over-the-top kill-everything weapon. Compounding my problem with the weapons is that none of the enemies are all that interesting to kill. The AI pathfinding is very poor with enemies regularly getting stuck on walls and doors. I have no clue how intelligent the enemies in Blood were because they were brutally unfair and you wanted them dead as soon as possible and had the arsenal to make that happen. The game also has two annoying enemies that really feel like they're put in to waste your time and ammo--a small spider-head that gnaws at your shins and a small flying head that does shoot at you, but is just a nuisance. Overall the game is fine but doesn't stack up against history or anything new like Project Warlock 2, Dusk, or Amid Evil.
The core game-play of stalking a target and killing them when the best opportunity comes along is intense and satisfying. The AI makes really makes the city feel like a self sustaining environment. The downside is that the game gets repetitive once you figure out the ideal strategy. This is a game with a pretty high learning curve and punishing difficulty so taking risks and being able to improvise with the mechanics is almost never rewarded and usually ends in death. Glitches and crashes are still part of the game but some patches have improved stability. What fun there is to be had with Metrocide, it's hard to overlook elements that seem less thought out that end up hurting the game. The pricing of objects seems high in contrast to the low, low fee you get for successfully completing a hit. And the way more difficult hits are priced aren't worth the risk for botching them. A complex hit can be several magnatudes more difficult that just a basic kill but only worth 2x as much--for how punishing the game can be, the more difficult hits just aren't worth the risk of getting seen by cops or bodyguards or even your intended target. The manual gives insight to the development and, while the passion is evident, so is the fact that no one really had a clear vision of what the game was supposed to be. This shows up with the mentioned buggieness and design decisions that could work more in concert with each other rather than in opposition. While the game is a mixture of elements, some that don't quite work, it does deliver on excitement and tension and I do like the game a lot--it's just hard to sing its praises without qualifying them, too. [played on Windows 8.1--paid $5.20 during GOG sale]
