The Xbox basically is a PC designed for TV screens - it follows the DVD-player model for video output, and it plays DVDs. The Xbox games are DVD-games.
The Xbox has:
composite video out (like RCA jacks on a VCR)
SVHS video out (like a DVD and some VCRs) - $10 adapter
Component video out (new DVD players have this) $? adapter
The resolution on my SOny 27" with SVHS in is very good - just like a DVD - I think that means 400 lines on my TV.
The nOrhtec PCs are in some ways similar to the Xbox - instant boot, no fan, will play DVDs or CDs.