The old stuff is MPEG2. 4 gig is about an hour. Most are in AVI containers. I had an old Hi 8 camera years ago and recorded those movies to DVD when I went digital. When I realized the discs were starting to go bad, they all got dumped to drives directly as ISO files.
The new HD stuff is all MPEG4. Some are in MKV containers, others are in MP4 containers. A few are even in DIVX containers. Unfortunately, I have a hodgepodge of legacy devices and I have to think about where I am going to use them before choosing. My newest gear will play all three.
Plus I have a number of shows recorded off the tuner on the computer. Those are on whatever format Media Center uses, those are MPEG2 and run in the 10’s of gigs, the Sound of Music was like 40 gigs! Those I convert if I want to move them off the computer. Otherwise they are watch and erase.
My historical experiences remarkably similar, even the HI 8 and DivX CODEC and deteriorating discs, but my platform has always been Linux with Mythtv for tuner capture and usually VideoLAN (VLC) for playback. I see VLC is available also for Windows. I am about halfway through organizing and renaming old videos and getting them ready for my mother’s digital frame.