The way sandbox games have developers, is the normal patterns for them is to go around and travel from point A to point B, and then do a linear mission at the point that is reached. It is still requiring level design and so on for the missions, to make them interesting. If the world is large, with a wide range of submissions, you end up with there eventually being repeating of what you are doing. This can get tedious, if there is not enough variety.
However, let me list several games akin to sandbox games, that I really didn't see listed above:
* "God games". I am think of games where you oversee a world that evolves and is organic in nature. The world is a sandbox of sort, but what happens is up to you. You can think of Simcity as an example. Another one would Civilization.
* Sandbox games like Crackdown or the Grand Theft Auto before GTA3. These are organic worlds you can jump into and do things in. There is no start or stop point. You have objectives, but how you get them is up to you. You can explore and find things in it.
* Western RPGs. Either you like them or you don't. They don't tend to fall under the sandbox category, but they function very much like them. Things you do have consequences, and there is a story. But, there is a focus on leveling up and developing a character. This leveling up angle drives one to grind. Without it, it is just an action game set in a sandbox. Also factor in the exploring angle in Western RPGs to. I would challenge anyone to find Mass Effect 2 boring also.
In this, I would count the likes of Borderlands, fitting between the two. For me, it wasn't boring, and I played it single player. I count it as the best game this generation that I played. And a slight detour here would be Miner: Dig Deep. it is an action resource management game, where leveling up, and getting better equipment, is interesting.
