If I were to take the first 25 episodes of Death Note and make a conclusion, I think I may agree that Death Note is the best anime. The anime was perfect up to that point: Right tone, perfect plot, outstanding drama, mind-boggling face-offs, excellent characters, cerebral action, full of adrenaline and list goes on and on... But as much as I love Death Note, gotta admit that there was a decline in the second part and it limped a bit till its finale. It remained a very good second part but definitely not on par with first 25 episodes.
That being said, Death Note was my No.1 for a long long time until Steins;Gate came. And if we were to remain in nearly similar genres comparisons, then Code Geass is very close to Death Note. Some will prefer DN, some will prefer Code: Geass - a matter of choice. Also, I'd like to mention Psycho-Pass - which is still pretty new but as time flies, it will soon be a cult one! There are similarities with Death Note; though also very different but given that it contain, imo the best villain in anime history - it's pretty high in my books.
So, yeah, I don't think Death Note is better than all animes...Let alone high difference or not! To be noticed, I didn't really compare it with other genres animes where there are lots of great animes in their own medium. Yes, it's great and surely ranks among the best nonetheless!