It's easy to convert practically any video format (including mpeg, avi, wmv, vob, divx and many more) to play on the iPhone using the Cucusoft iPhone video software. I downloaded the free trial version at iPhone Video Converter Software Reviews.
I was able to convert DVD to iPhone using the Cucusoft iPhone Video Converter software I found on Popular softwares online So far, I'm really impressed with how easy it is to use and how effectively it got the job done.