As above you will want a tool that can peer into the files. I also liked le fluffie if you have standalone files (most things you download regardless of JTAG, demo or some old profile sharing thing), if you have XTAF to go through first (what you will get if you copy things to USB as formatted by the xbox) then you need something to handle that as well.
Once you are in though then all bets are off as far as formats used -- I pulled apart one of the ports of Doom once and it was half almost standard Doom WAD and another some custom archive to sort the audio that was almost standard midi, other things resemble mainline 360 games in their makeup, others more standard PC formats for the time, others straight up image formats that would load right into GIMP or 3d modellers*, others the sort of thing I link
https://wiki.multimedia.cx/index.php?title=Category:Game_Formats http://wiki.xentax.com/index.php/Game_File_Format_Central for.
*the 360 was primarily a 3d machine so there is a lot of stuff that plays to that, even if it looks 2d. To that end sprites might not be the right term.
Audio wise aside from MID above the 360 did technically support a take** on WMA (Microsoft pushed format for audio, not as popular today but was back then) in hardware so many things would have gone for that, though at the same time if the PC version of whatever game was being ported to XBLA used some game format (see links above), some open source format (OGG/OGM being reasonably popular for some things) or just something more basic then
**I don't think we have a full spec for it, though it might have come in the leaked SDKs. It was mostly a cut down version (not like you need human usable metadata/tags), and probably won't have DRM issues but might need you to go on Windows media player of a marginally modern at the time version rather than hoping whatever freeware thing you have to sort WMA plays nicely.