See, the game engine you would want to use would first depend on what programming/scripting language you would use. There at hundreds of engines out there, but not all of them support every programming language.

If you are going to go with C# I recommend unity3d(http://unity3d.com/). I dabbled with unity a few years ago and it was ok. Its a 3d game engine but I have seen many 2d games built upon it. Unity works as an installed program, as a web game (though the user must install the unity runtime), or for iOS/Android.

If you fresh out of college (or in college) they probably taught you Java. That's good because Java is a very popular and flexible language. It is possible to write 2d and 3d games in java using the Lightweight Java Game Library (http://lwjgl.org/). It works on most platforms and is somewhat easy to use (the game engine for the popular game Minecraft is built atop lwjgl).

If you are a C/C++ dude, then there are tons of choices. The one drawback is that most C/C++ engines don't support embedding the game in a webpage. Though upside though is that they are some of the most powerful engines around.

If you are a well educated programmer who has a great knowledge of the language of your choice, the easiest way to go might be to just write your own engine. Yeah, sounds like a lot of work, but in the end it might be just what you need. I mean, you (and whoever helps you write the game) can make the engine just the way you want it. Game engines are complex projects, but after a lot of studying and testing and analysis of other engines, you'll get the hang of it (I've written 2 engines, the first one I wrote for a small unpublished flight simulator; my current engine is a FPS engine). Oh, that reminds me. If you do happen over an engine that makes you say "This is the engine I'm using" that is usually one drawback, genre. Yeah, just think of it this way, its easier to find a RTS game engine than to modify an FPS engine to create an RTS game. So just because you like the way the classes and namespaces are setup in a certain engine doesn't mean it will be the most efficient one for you (this is where creating you own engine usually gets re-added to your list of valid options).

A few other engine I recommend include:

Panda3D (C++ & Python 2.6; http://www.panda3d.org/)
LOVE2d (Lua; http://love2d.org/)
Delta3D (C++; http://www.delta3d.org/)

Oh, also, not to get your hopes down, but to create an MMORPG game requires thousands of dollars in funding. Think of all the servers you will need to maintain the huge database of players. Why do you think most MMO games are released by larger game companies that already have a large amount of infrastructure. Even if you were to create an FPS like Call-of-duty, you would still need a large infrastructure to keep track of all the player stats.

Sorry, but MMORPGs are not designed for beginners nor are the designed for experienced indie developers. You would need a team of veterans who know exactly what they're doing to get everything working right.