Some of the higher profile (and often subsequently better) shows have some really good voice acting. Ghost in the Shell: Stand Alone Complex is one that comes to mind. The Japanese acting is excellent, but the very fact that they talk so much may make it hard on the eyes when you read the subs. The English dub for it (which I saw first anyway) is one of the best I've heard.

Some shows' original voice material is so much a part of its definition that no matter how good the dub is, it won't do it proper justice. Haruhi Suzumiya's English cast does an outstanding job for the majority of the time, but the original performances of the two main characters is a large part of what makes the show. Gurren-Lagann is another show where there are a few performances that will be impossible to match.

Most shows I've seen from the last few years that I've bought on DVD didn't have any particularly excellent Japanese acting that made me prefer it unconditionally over the English dub. For Gankutsuou in particular (which is one of my top anime), save for Jouji Nakata's 'Count', I find the English cast to actually perform better.

Then again, I tend to skew away from simpler, younger-oriented fare like Naruto, so I don't get exposed to much of the type of dub that attracts.

My recommendations in this thread are leaned more to the 'fresh out of Japan' side, which makes it easier for me to choose from instead of all the stuff I've ever seen. So, Gurren-Lagann, Dennou Coil still have my vote. Would be nice if Auragaea would come back and tell us what was seen.