Yes, sometimes the scene seems to be a bit asleep... but there are still a lot of developers working, who are not going to let the Xbox die

I use to read posts from some of them sometimes here, but this time the post of Madmab said all that can be said, so I guess that nobody had anything to add. I only added the information of the particular case of the Jag, as it was different (port of an old version).
The status of the Jaguar emulator nowadays is not marvelous... I began the port keeping in mind the following idea: "ok, at the moment we don't have any Jaguar emulator, so anything that we achieved, will be better than nothing". First of all, you must know that the emulation of the sound makes everything go slow, so I added the following options: play with no sound, play with real sound, play with overclocked sound (x2, x3 or x4). Then:
1) If you choose playing with NO sound, you can play at fullspeed (with no frameskip) to some games: Rayman, Zool 2, Sensible Soccer, Cannon Fodder, Flashback, Pinball Fantasies and a few more. Other games go slow, and other games don't work.
2) If you play with real sound, everything go slow, so you must use frameskip. For example, Cannon Fodder with real sound needs Frameskip. But as you know, if you use frameskip, the animation looks a bit worse.
3) The other option is using overclocked sound. Overclocked sound plays sound at a good speed, but at low quality. For example, Cannon Fodder can be played with overclocked sound x3 at full speed, and with no frameskip. The SFX sound near perfect, but the songs sound bad. As the gameplay of this game has only SFX (argh, bomb, bang...), I think that it is a good idea to use overclocked sound with it.
What is the best option? It is subjective... For example, I prefer to play Cannon Fodder with overclocked sound: it plays well and at full speed, although the sound is not good. Other people prefer the second option to have good audio (and bad animation) and other people prefer playing with no sound.
Recommended games that play well in this emulator: Rayman!!! Plays very well (I prefer without sound) and it's a very good game. Some people reported that the savegames don't work, but it's not totally true: the savegames work if you exit of the game properly (with START+BACK) but if you turn off the console, the game is not saved. Other very good games that work well without sound are Zool 2, Flashback or Sensible Soccer. Cannon Fodder plays well with overclocked sound x3, the same that Pinball Fantasies (other good game!).
Finally, as you asked by the most famous games: Alien vs Predator can be played at full speed if you select no sound and Frameskip 1 (it looks very well). Maybe overclocked sound can work too, I don't remember. The gameplay is good but it has a very bad bug: the map is not shown properly when you select it, so it is very difficult to advance in the game. But if you don't need map (maybe if you have it printed in paper) or if you simply want to run and shoot aliens, you can enjoy it.
Cyber Morph does not work, and Tempest 2000 works but it runs very slow even without sound. So, if you want to play Tempest 2000 you have to select "no sound" and besides a big frameskip
Finally, the emulation of the joypad: Virtual JaguarX emulates the directional pad (with the joystick), the A-B-C buttons of the jag (with the A-B-X buttons) and the numerical pad of the jag too (using the buttons Y, white, black, triggers, and every direction of the Xbox dpad). The only buttons that are not emulated at the moment are the * and # buttons, but they are almost not used in real games.
If you finally decide to test Virtual JaguarX, please keep in mind what Madmab said: the Jaguar is a console of the 32/64bit generation, and the Xbox is having a hard time trying to emulate it, so don't expect a perfect emulation like the one that we have in the emulators of the 8-16 bit era...