Do you want the "best" quality or something more convenient? Anthony gave one perfectly valid solution, but there are others that don't cost anything.
RipIt4Me can decrypt, rip and shrink your movie to fit a dvdr disk---at no cost to you. Quality would be equal to that of AnyDVD + CloneDVD. You might want to adjust some settings, main movie only for example, but you should read the guides for RipIt4Me to find all the variables.
If you want the absolute best quality, that means splitting to two disks, or burning to dual layer (which you have already ruled out). DVDShrink can easily split a dvd to two disks in reauthor mode. Use RipIt4Me to get the dvd on the hard drive with NO compression, then split it with Shrink. Pretty easy to do. There is a guide for this procedure over at mrbass.org
And here is a compromise solution. Use RipIt4Me to decrypt to the hard drive with no compression, then use DVDRebuilder (free version) to reencode the movie, or parts of the movie that you want. Using the HC encoder that is included with the program, you get a slightly better result than you get with transcoders like Shrink or CloneDVD, especially on large dvds. The only downside is the length of time it takes to run this program. I normally let it run overnight while I sleep, so this isn't a problem for me, but it is inconvenient for some.