It might be illegal? I mean, it is distributing copyrighted property without explicit consent. I know other free things on the Internet sometimes have disclaimers stating who is allowed to distribute them. See them on FAQs and license agreements from time to time. But that's legality.
[EDIT: Ah. Other people answered this better-^]
Ethically, there are probably reasons why a person might want to control distribution of a freely available game. Maybe they want to make sure players have to visit their website, for instance. For publicity reasons? Some might see having to ask you to take their games down as an inconvenience that they shouldn't have had to go through to begin with. Not saying it is a practical or enforceable stance, but there are people who think this way, and you would run the risk of disrupting their interests.
Personally, I would be grateful to have my games reach a wider audience, and free hosting is always a plus, too. I would probably appreciate being asked first, as a courtesy, though I don't think I would feel slighted if I weren't asked. MAYBE I would if I weren't credited, but I would make sure my name was all over my stuff anyway, so anyone who cared who made it would know.
I haven't been following this Nexus thing, so I don't know how it is supposed to work. But if you don't want to step on toes, I would contact the authors of games before uploading them, and also provide links to their websites (if relevant) next to the downloads. That way the worst thing you can be accused of is an unsolicited e-mail.
But of course that could get inconvenient for you or whoever has to send the e-mails, and a lot of people probably will never get back to you. There is an argument to be made that the service you provide by hosting a comprehensive list of games outweighs whatever ruffled feathers might come from hosting someone's game without permission, and you are unlikely to get into actual legal trouble, I would think. It just wouldn't be an ethically spotless argument.
[EDIT: Ah. Other people answered this better-^]
Ethically, there are probably reasons why a person might want to control distribution of a freely available game. Maybe they want to make sure players have to visit their website, for instance. For publicity reasons? Some might see having to ask you to take their games down as an inconvenience that they shouldn't have had to go through to begin with. Not saying it is a practical or enforceable stance, but there are people who think this way, and you would run the risk of disrupting their interests.
Personally, I would be grateful to have my games reach a wider audience, and free hosting is always a plus, too. I would probably appreciate being asked first, as a courtesy, though I don't think I would feel slighted if I weren't asked. MAYBE I would if I weren't credited, but I would make sure my name was all over my stuff anyway, so anyone who cared who made it would know.
I haven't been following this Nexus thing, so I don't know how it is supposed to work. But if you don't want to step on toes, I would contact the authors of games before uploading them, and also provide links to their websites (if relevant) next to the downloads. That way the worst thing you can be accused of is an unsolicited e-mail.
But of course that could get inconvenient for you or whoever has to send the e-mails, and a lot of people probably will never get back to you. There is an argument to be made that the service you provide by hosting a comprehensive list of games outweighs whatever ruffled feathers might come from hosting someone's game without permission, and you are unlikely to get into actual legal trouble, I would think. It just wouldn't be an ethically spotless argument.