Neuschwanstein Palace has little of historic interest unless you are interested in the history of tourism. It was built as a palace in the late 1800s by a largely insignificant king (except for tourism) but is an architectural masterpiece with a lovely setting on the edge of the Alps. The problem with most "real" castles in Germany is that they were allowed to fall into ruin and were quarried for stone before the time of historismus in the 1800s when many were rebuild, sometimes with fanciful plans that didn't resemble the original ones. Haut Koenigsbourg in Alsace, France was rebuilt in the 1900s, making it even newer. Others, over time, were converted to palaces that may bear little resemblance to the former castle.
There are probably 100s of routes throughout Germany based on one factor or another. For instance, if you are interested in the Staufer emperors who ruled to as far away as Sicily, there is a route in Baden-Wuerttemberg based on them. There are others such as the Swabian Poets Route, Half-Timbered House Route, Fairytale Route, Tree-Lined Roads Route, etc. so if you search hard enough, you might be able to find something of particular interest to you.
There is no lack of historic places to visit in Germany having over 30,000 castles and palaces alone, and anywhere in Germany should have at least a week or two of excellent things to visit there and nearby, if not months' worth of them. The German state with the most listed historic buildings is Baden-Wuerttemberg ( http://www.tourismus-bw.de ) followed closely by Bavaria, and for tourism they are numbers 1 and 2 but in the reverse order. Together, they probably have about half of such buildings in Germany. Both of these states are located along the southern edge of Germany, and because Baden-Württemberg is much smaller than Bavaria, its concentration of historic places is much greater.
http://www.schloesser-und-gaerten.de has information on the excellent castles, palaces, monasteries and gardens that the state of Baden-Württemberg operates. All websites I have given can be changed to English, and if you look at the individual sites in this website, it has anecdotes about each place along with other information. I can highly recommend the 3 medieval monasteries UNESCO Maulbronn, Bebenhausen and (Gross)comburg), all are well-preserved and delightful to visit. The Residenz in Ludwigsburg is Germany's largest perfectly-preserved (all original, not a post-War rebuild like too many places)) palace which has the original furnishings throughout its history and several different architrectural styles as they changed with time. It has the longest (1.5-2.5 hours) and best palace tours that I've had in all of Europe and I've seen quite a few palaces, just make sure that you take the once a day early afternoon English one as it is better than a tour in German. The impressive fortress ruins Hohenneuffen has excellent views as it is built perched on a tall steep cliff edge. The largest castle (fortress) ruin in area is Hohentwiel with excellent views over the Swiss Alps.
Our favorite town in Germany to repeatedly revisit is Tuebingen ( http://www.tuebngen.de ), just quintessential Germany with its hilly cobblestone streets, half-timbered houses, castle, interesting nontourist shops, one of Germany's oldest universities, and the nextdoor delightful medieval well-preserved Bebenhausen Monastery which also has some more modern history being the last residence of the King of Württemberg after he was forced to abdicate following WW-1 and also the seat of post-WW-II government for combined Württemberg and the Hohenzollern Prussian lands. Just south of there is Burg Hohenzollern ( http://www.burg-hohenzollern.com ) which is the rebuilt historic seat of the Hohenzollern family of Romanian and Prussian kings and German emperors.
Just a few ideas of excellent places I always enjoy revisiting in this part of Germany. For some other ideas in the area, have a look at what I wrote in #1 of http://www.tripadvisor.com/ShowTopic-g187275-i116-k6068438-Stuttgart_as_a_base-Germany.html#49932873 .