It's an older incarnation of mostly the same game.
What I think is great about TES games is that they have a sort of "formula" to them that doesn't actually have to be changed in order for the game to keep evolving, as it relies almost exclusively on technology to keep itself current.
Oblivion really shows you how far technology can come in the same console cycle, and how much having experience with that technology effects how well your games are made. The gap between Oblivion and Skyrim is HUGE, because you have Fallout and New Vegas and anything else Beth's worked on between the two, that used pretty much the exact same formula as TES.
I still like Oblivion, but I'd never play it to death like I do Skyrim now. If any reason, I'd just play it for the continuation factor, or to see the main quests again and relive the lore, which even ten dozen books in Skyrim wouldn't be able to make you truly feel how epic it feels when you are actually there.
"A thousand travel books aren't worth one real trip." if you know what i mean. If you think Oblivion is inferior heavily to Skyrim, it's a good thing, because that shows how far the series has come in terms of quality.