Aliasalpha: Hmm theres a thought, wouldn't the xcom games go great for the xbox arcade?
Shoelip: Not to be rude but; how?
Well first and foremost I'm glad you're not being rude, it's a rare thing to find on the internet, thanks.
If anything, I think that the xcom games (at least 1 & 2, I never found Interceptor) and other turn based strategy games are one of the few game types where conversion to a console could retain a nearly identical experience.
The Xcom games are turn based so accurate and fast mouse movement like you get in an RTS (and dismally fail to get in a console RTS) wouldn't be needed. The in-mission movement & targetting is already based around a box system which would work perfectly well with either the analogue stick or the dpad.
Secondly the 360 (and presumably ps3 but I've not seen it) controller has a good number of buttons letting you map a lot of normally icon based commands directly to a button input. Failing, that a single button press could change focus from the main game screen to the different command panels, say the action bar thing where you tell soldiers to kneel, go upstairs, reserve APs when moving or change the view. Accessing that bar in this hypothetical version would simply highlight the icon and pressing A would have the same effect as a left click. If I was designing it myself, I'd probably map changing the view height to up & down on the dpad and next/previous soldier to left & right because those were the non-combat controls I used the most by far.
The one major area where you'd NEED to change to keep a good flow of gameplay would be the world map, particularly for UFO interceptions, however there's 2 ways I can see of keeping the majority of the functions. First you could assume that the player is only going to deploy craft for intercepts and recovery missions, if you did that you could have a list of targets pop up when you access the craft in question and it'd fly to it without having to manually click. The alternative is to allow the creation of waypoints for the craft to fly if you wanted a patrol. It could also be good to implement a pause time command system when the player accesses the craft, this could allow for the careful selection of waypoints or targets without punishing them for the lack of combined speed & precision that a controller just can't give.
Other than that it'd be a copy & paste of the gameplay. I see no reason that base building, research and all the other features can't remain identical. Sure the konsolekiddies might bitch that it's slow and boring but add an updated graphics option with pretty explosions and their minds will be occupied by the pretty flashy things for hours.