mystral: For the open-world games without level-scaling and still way more interesting and challenging combat than Oblivion, see Gothic. Or Risen. Or Divinity 2. Or even both Two Worlds.
It's perfectly possible to do it, plenty of games have managed it, Bethesda was just too lazy to design their game around it, because it obviously takes more time and effort to assign a level to every enemy type than to give them the PC's level.
mutishev: The only game compared to Oblivion open world mentioned by you is Two Worlds even thou monsters don't respawn there and there are "locked" areas where you die in seconds if you enter.
Divinity 2 is linear, pseudo open world game.
I want to say that those games are one time, play through story, do some side quests and repeat the process, Bethesdas games, can be played as long as you wish, you can revisit caves, towns... Thats why monsters level with you or you will one shot them when you get stronger.
I can't see sand box game without some sort of scalling, I bet Skyrim will have one too.
Just because some areas are too hard for you to beat at first (which is the way it should be imo) does not mean the game isn't open world. They just prefer having a realistic world to satisfying people who want to be able to go everywhere (including the final boss dungeon I suppose) from the beginning without suffering any consequence for it.
In a game with a levelling system where you're supposed to get stronger, it just doesn't make sense.
The Bethesda's games need level scaling part is wrong. Morrowind wasn't like that (it had level scaling but it was limited, only affected which monsters would spawn, and it didn't go past lvl 20) nor was Arena or Daggerfall.
In fact only Obliviion features that kind of level scaling, they scaled it down for Fallout 3, so you're probably the only one who though it was a good idea.
Second, I'm sorry but to me monster respawning is a bad mechanic unless it only occurs in some areas for reasons that are clearly explained.
What you want seems closer to me to a single player MMORPG than anything else. Basically the player never makes any real difference to the world he's playing in, since no monsters will ever die for good.
And yet, guess what? MMORPGs don't have level scaling either. You can still play them pretty much forever if you want to.