I get what you're saying. But a lot of great games have borrowed elements from other game series. I mean, look at the effect LOTR had on Fantasy as a genre.
Also, it wasn't even the same game studio. Obsidian made New Vegas, Bethesda just QA tested and published.
Actually, I don't like games 'borrowing' from other games. I get what you're saying about Lord of the Rings, but the really
good fantasy that came from that was influenced by it and let it inspire their writing, instead of ripping characters and ideas straight out and implementing them.
Case in point: one of the biggest poaches I've seen in Skyrim is the marriage system. This was implemented, in my opinion, simply because it's become popular in other games like Fable. Instead of straight out ripping them off, they could have considered developing the follower aspects a lot more, and leading some of them to have romantic possibilities. It would have added more depth to the followers and it would have given us the opportunity to discover these surprise romantic opportunities instead of them just saying "hey, wear an amulet and stuff, and people will fall madly in love with you!"