Which 3D game engine is the best for my needs?

[Wolf]

Been thinking of an RPG/adventure game. I've heard of some like Irrlicht, Ogre3D and Microsoft's XNA. Or perhaps some existing game engine?

I could probably do 2.5D opengl from scratch using isometric perspective with depthmaps and stuff like that, but I think 3D ( although character modelling is not my best) would be a bit more versatile.

What would be the easiest to start with?

It could be C/C++, but it could be anything else. I want control over everything, I don't want to be restricted by dumbed down menus and all these unnecessary things. So if I don't like something standard, I can add custom things easily. But on the other hand, I want easy content creation (by easy I mean not harder than creating paks with bsp maps, sounds, textures, etc. for q3) so I could focus on the story and characters and stuff like that, making maps, cutscenes possibly, etc.

What I don't really require is best graphics in the world; I want it to be realistic, but not over the top. I'm thinking q3 is maybe too old but maybe some newer incarnations? Then again modifying existing deathmatch code to suit an RPG feels like a bit more pain in the ass than creating it from sctratch...

[Parts]

Unity might be worth a look.

[GypsyLlama]

Multiplayer\co-op?

[Wolf]

Multiplayer\co-op?

At first I want to experiment with graphics. For multiplayer, any decent network library should work. I'm not aiming for mmorpg or something massive.

[GypsyLlama]

I am totally ignorant about what you're talking about doing, but you may want to check out whatever engine was used in Neverwinter Nights 1+2, good game, good engine. I suppose the only variable is if you have access to the engine source code or w/e.