Oblivion was my first TES game, and my first RPG experience in fact, so I still hold it close to my heart - despite all of its shortcomings and flaws.
I still have it installed on my computer and was playing it when Skyrim came out, so I put that character on hold. Once I got tired of Skyrim (after 200+ hours!

, I went back and played Oblivion for a while.
You know when parents say that "they love all of their children the same"? I feel like that with TES III, IV and V (haven't played anything earlier than Morrowind). I love all of these games just as much, but in slightly different ways.
I think that we are fortunate to have all of these games available to play. Whether you prefer one to the other, each can provide you with hundreds of hours of entertainment and great replayability!
By the way, while I think mods are wonderful in Oblivion and will most definitively augment your gameplay experience, I also feel that the only truly necessary mod is the Unofficial Patch. Everything else is cosmetic.
Also, if you're considering playing Oblivion for the first time, by all means get the GOTY or 5th Anniversary version, which includes the Shivering Isles; that expansion is the best thing that ever happened to that game.
Morrowind is also such a wonderful game, and I would strongly recommend the Morrowind Code Patch. The MGE (even if you don't enable the purely optional 'distant view') is also good to have.
Just the same, make sure you get the Bloodmoon and Tribunal expansions.
I think Skyrim is a terrific game despite all of its problems and flaws, and I suspect it will only get better with time, especially if you are on the PC because of all the mods, the Unofficial Patch, and surely any DLC/Expansions we get.