If it helps, I have a 32GB itouch and it currently contains:
2500 photos
600 songs (40% Apple Lossless, rest in 320mbps AAC - Apple lossless is about 3 to 4 time the storage of the AAC. You can know the AAC down to 128mbps if storage is of primary improtance and hold thousands)
5 Movies (several the highest quality video available from vedeora website, the rest at a high but not highest quality quality)
Complete series 3 of Red Dwarf
3 music videos
and I have 15.5GB free so just under half full. you can fit alot more on there too if you cut back on the quslity a bit, but I like the picture to be immaculate. I like to get the best sound I can get too. There players out there with more storage and some with better sound, but none that are such a good alrounder and especially none that are as good with movies, yet still small enough to comfortably put in your pocket.
I hope this helps
John