Vassal will not enforce rules for you, but the modules basically give you the pieces you need and the board. Great tool for trying out games with friends before making a purchase on something more expensive.
Arkham Horror is definitely a favorite. In that vein but with a shorter playing time and less complexity is Elder Signs also.
Eclipse, not gonna lie, is extremely complicated. My friends and I actually prefer playing that one electronically because of the crazy number of pieces the physical game has and the fact that rules are automatically enforced properly.
I assume you guys have also heard of Vassal? Great open source engine for trying out board games before you buy.