I haven't seen too many of these so I can't say my opinions are accurate of market value.
What's tough about MvC2 is that it had such a perfect port to the Dreamcast, that you can essentially own the game for $50. That said, I have seen an MvC2 cabinet on ebay as a buy it now for $750-800, but the guy listing that auction kept relisting it (almost 10 times over at 30 days per auction). I'm not sure it ever sold at that price. This particular auction was for an MvC2 in a non-Capcom cabinet, meaning that it was one of the kits where another fighting game was refitted as MvC2 using the kit.
MvC2 is on my list of "games I'll own someday." Honestly, I'd pay $500 for it in a Capcom "Big Blue" cabinet that's in perfect condition. I'd pay up to $300 for a non-Capcom cabinet, like the one you have, depending on the condition of the cabinet. Like I said earlier, you can own the game for $50 so I feel like I'm just paying for the quality of the cabinet it comes in. In a non-Capcom cabinet, it really comes down to cabinet aesthetics. If the cabinet looks appealing to me, I'd be willing to pay a bit more.
Once again, this is just my own opinion. I believe that MvC2 is the best 2D fighter there is. Greatest game with lots of memories playing it with my best friend. But if I were to own MvC2, I'd want to "go big or go home," meaning I want it in a Big Blue. I would probably turn down the opportunity to buy your MvC2 with the hope that I'd find it inside a better cabinet some day in the future.
All this considered, if I were local and the controls and monitor were in excellent shape, I might offer you $300. If you took it, I'd walk with the cabinet, and if you didn't want the $300, I'd just walk.
Good luck with your sale. Awesome game.