Are you familiar with the importance of input lag? Unlike CRT's, all LCD's have measurable input lag. Explanation here:
http://www.displaylag.com/what-is-input-lag-the-breakdown/Input lag is highly detrimental to gameplay. No matter what type of game, if there is anything that you have to react to unexpectedly, any kind of delay will degrade your ability to react. There is lag in MAME's emulation, lag in the LCD, and your own response time. None of these "cancel out," it all adds up.
You may not immediately notice the difference this causes if you don't have a low-lag setup that you're used to too, but whether you're aware of it or not input lag will cause you to not do as well in the game as you would with less lag. It will also cause a general feeling of less responsiveness from the controls. If you play an emulated arcade game on a poorly configured setup, then go play it on a real cabinet, you may notice how much "tighter" the controls feel on the cabinet.
People will try and tell you that it's not noticeable, but this is usually because they either don't know what they're missing, or they don't want to believe that there is something they're missing and that work is required to fix it.
Lag in MAME can be reduced significantly by using the right build with the right settings. As for the display, if you don't want to use a CRT, low lag LCD's are available. Most LCD's lag several frames, and are very poor for gaming. Manufacturers know this, but they are primarily focused on making TV shows and movies look as good as possible, as that is what their primary market wants. Sometimes there are game modes available, but this doesn't necessarily guarantee low enough lag for proper gaming. Input lag measurements aren't advertised (response rate is NOT a measure of input lag), so you need to know the model numbers of confirmed low-lag LCD's to get something appropriate for gaming.
Try starting here:
http://www.displaylag.com/display-database/This lists displays ordered by input lag, measured in milliseconds (ms). When running at 60Hz, meaning 60 frames per second, each frame is 16ms. I wouldn't recommend any display that lags more than two frames (32ms) for gaming, especially when adding MAME's input lag. With several frames of lag you can start to feel it just moving around in-game.