I am very much into my games of every type (except sport sim perhaps) and STALKER is utterly superb!
First thing I will say is that it 'feels' a little rough around the edges, but you will realise that it's actually beautifully balanced. Some of the weapon models look a little funny. There is no satisfying squelchy sound when you make a knife kill... a few tiny things like that are present.
But around this, you have a massive, excellent game. Time passes realistically. The game is very open-ended, you're very free to roam. Graphics are decent. The way the environments' have been modelled is very believable in look and in scale. You are restricted from certain areas by either fences or impenetrable radiation presence. (keep walking along and you'll soon die of radiation exposure) No invisible walls here!
'Anomolies' exist which are mostly nuclear-related, gravity-based 'traps' to steer clear of.
This game is dripping with atmosphere and the combat is brilliant. Guns are not accurate like they are in almost every other game I've played and they fire very realistically. Firearm combat can be tough, especially against multiple opponents, but if you like your combat 'real feel and convincing, it's brilliant. It's not a case of line your crosshairs over someone's head, pull the trigger and watch them flop; over range, the chances of your bullets going where your crosshairs are, slim; you'll be going for middle of the body a lot and may get headshots by accident because that's just how the accuracy is...
You will have to eat at certain times of the day.
When you get shot, you will have a colour coded 'bleeding' icon appear. What happens if you lose blood (and health) based on the severity of your wound (red icon = heavy, fast loss, green = low loss, yellow/amber = moderate loss). You will continue to lose health until you use bandages or medkit etc.
Everything has a weight. From an individual bullet to grenades, medkits and food. You can carry up to 60Kg (after that you can't move or jump.)
You have a meter for fatigue, which depletes slowly, but if you carry 50-60Kg it will deplete very quickly and jumping takes a big chunk. The stamina meter replenishes when standing still.
You also have a 'noise' meter, splinter cell style, helping you to be stealthy and quiet when you need to and there's a third party 'awareness' meter so f you've been spotted, you'll know about it. You can use these to great advantage in close combat situations.
Weapons are wide ranging and very authentic with many different bullet/round options for the same gun. Sometimes you will need the armour piercing rounds and sometimes the high damage ones. Sometimes the shotgun shells that have extra range or the powerful spread type etc. etc. All in all, the way weapons are dealt with in this game is superb.
AI is excellent and enemies can be very sly. They don't rush in and mostly work well in teams. You'll have your work cut out. Stalker often feels hard... but never unfairly so. You never feel like the computer's cheating, or making it unfair through health handicaps. You know you just made a bad call or got outnumbered or jumped when you didn't expect it.
Missions are fairly varied and the gameworld is large with various factions who have different ideals, agendas and inter-faction relationships.
There's SO much to this game, so many brilliant details and so much thought as gone into it. I am really so impressed and very embarrassed that I left it sitting on my shelf for months before I decided to install and play!