Filming/videoing an Amiga game by pointing the camera at the screen is probably THE WORST way to capture the video. The quality you are going to get is utter crap - blurriness, video frame rate banding, room reflections and glare off the screen - so if you're going to do it that way it doesn't matter what kind of camera you are going to use - might as well get the cheapest one possible as it will look pretty bad no matter what.
It would be much better to either:
a) Play the game in WinUAE and record the gameplay to an AVI (this is a setting within UAE)....the AVI can then be imported into an video editing software where you can add your own music or voice
b) capture from an A1200/A4000's/A520's colour composite video output (the RCA video jack) to a USB video capture device hooked to your PC (these are cheap), or to a stand-alone DVD burner, or to a camcorder that has a composite video input jack (there are lots of these).
If you're really set on buying a camcorder though - I too would recommend miniDV. Sure, it's not as convenient as a solid state camcorder. For instance it's tape, so you can't drag and drop the movies to your PC through USB. You have to use a (cheap) firewire connector and copy them over in real-time (digitally).
But, like others have said, those new Hard Drive or Flash Card video cameras use a fairly agressive video compression algorythm which actually is worse looking than the very mild video compression used by miniDV. Of course, this depends on whether or not you have the ability to actually see the difference. For YouTube videos ending up as heavily compressed Flash Video it might not matter anyway.
If you're talking HD video, well then, you probably can get a Flash card based camera that would beat miniDV, but it's going to cost you a LOT more. You don't really need an HD camera for something that's going to end up on YouTube - also almost no Amiga games are in HD resolution.
I think there are HD miniDV camcorders too but they are pro-level and VERY expensive. A standard-definition miniDV camera will do you fine - just make sure you get a model that records in both the old 4:3 ratio and the new 16:9 screen ratio. You'll want the old ratio for the Amiga screenshots (which were all 4:3) and the new 16:9 ratio for everything else.
The other advantage of miniDV is that - because most people are switching over to solid state cameras (most people care more about convenience than quality) the miniDV cameras are very cheap now (among the cheapest you can buy).
I would recommend a Canon or JVC miniDV camera if you go that route.
