Sprites in a 3D game look horrible for most objects: buildings, characters, terrain. Sprites are typically used for particle effects, grass, or objects that are far away. The latter is often used a performance optimization.
AoE 1 and 2, yes. AoE 3 is 3D. True 3D works fine for RTS games and generally looks better, and can apply dynamic shadows, physics, etc. If you are simply saying that you prefer the old-style graphics, then okay. But your initial statement wasn't worded well if that is what you meant.
