Whether its ported from last gen or next gen consoles. How does a PC gamer know whether its ported from console or not? Usually ports from consoles are lazy and not optimised to take advantage of the PC hardware so they just look like emulated console games running poorly on a PC.
Is there a website that states whether a PC game is ported from a console or was the game developed on PC first?
Sooo..you answered your own Titled question.
As for a site that lists all games and if they're ports or not,I've never heard of one. That would take a good bit of work and research for such a niche use.
Are you not going to play a game because it's a port? I wouldnt let that stop me.
Can you not play a game because its a terrible port(GTA IV)? If this is information you seek,it will be EVERYWHERE if you just google the game name.
You know that a game is a console port by many things. But in general - poor graphics, only a few options to change graphics and sound options, FPS cap (I've thrown out many games due to 30 FPS cap), awkward controls, very poor performance on otherwise good PC etc. etc.
The best way to check for a specific game before buying it is to probably try Wikipedia and see what platform the game was initially developed for etc.
Also a good place to check is games forums - For example Steam's specific game forums.
As with anything always check before you buy. Like if you Google for example "The_game_you_want_to_buy_title - Problems" and you will always find out if it's a port because hundreds of people would be commenting it.