What's the best match iTunes version for iPhone 2G (first generation) now?
I'm not sure there is a 'best match' version.

The earliest version that will support an iPhone 2G to iOS 3.1.3 [the latest the phone can use] is iTunes 9.2.1

But I know of no reason it shouldn't be recognised by the latest iTunes. v12 still recognises my old 3G &amp; even has no trouble with my seriously ancient iPod Photo from 2004, which is still going strong as my in-car player.

I've seen suggestions to completely uninstall &amp; reinstall iTunes - but no conclusive proof it really does anything useful.

I also came across this whilst Googling - don't know if it still works, but might be worth a look - You Can Now Install iOS 5 On iPhone 2G/3G And Old iPods Without Jailbreaking