Painkiller is a great example of how to make an retro fps in this gen and i highly reccomend it.
Visuals in painkiller looked really good in 2004 and in my opinion they still look good. the modeling is very well done,animations are good,texture work is impressive in bits, and the lighting is great. now one of painkiller's best aspects are the looks of the levels each level is different from one another making the game's levels feel varied. The enemies and weapons has some pretty bad ass designs especially the monks there is also a good amount of detail put into them.
Sound in this is also top notch on the one hand you have great sound design your weapons sound beefy and concussive and dismemberment is fun and satisfying to listen to. voice acting is decent but there is very little of it. now what makes the sound so great is the music now i think it you should know i'm a metal head and this game has very awesome metal tracks when there is a battle it gets you pumped like a proper action game should.
Story is that daniel and his wife end up in a car crash and daniel ends up in purgatory because he wasn't good and enough and god needs daniel to destroy lucifer's generals. story is basically a reason why you are killing demons. now granted the story doesn't make any sense but who gives a shit and **** plots in a fps because they matter as much as what type of tie you are wearing to work.
now the gameplay in painkiller is pure old school fps fun! shooting demons and monsters feels rewarding and such. now what makes painkiller really good are the weapons all the weapons have 2 firing modes and add a special thing called variety you have a rocket launcher/chain gun, a shot gun that can also freeze enemies, and a gun that shoots shurikens and lighting originality this game has it. picking up health is rather unique you see when you destroy an enemy their soul will be there for a while and you of course gain more health however if you collect a certain amount of them you will turn into demon mode which is basically an insta kill power up and it makes the killing so much fun. in terms of difficulty. In each level you can earn gain several cards by etheir completing a level with only the painkiller or get all the souls and these cards can help you a lot with abilities like additional health and such. the game is rather lengthy there is a lot of levels in this game. there is also multiplayer however there isn't many people playing however from what i have played it was fun. if there was one problem with painkiller is that it can get repetitive in parts. painkiller is like the unofficial doom 3 since the actually doom 3 slipped and banged it's head on the kitchen sink and forgot it wasn't system shock( if you zero punctuation you'll get that reference) and quake 4 was slow and monotonous and hardly felt like quake. painkiller is what doom 3 and quake 4 should have been, fast paced old school simple metal fun. Painkiller is easy to find you can get it for 10$ on gog and steam for that price it's worth it.