I purchased this route a couple of weeks ago and love the scenery. Are there any other routes with similar scenery?
Scenery speaking, I would guess none look exactly the same, but probably the old Main-Spessart Bahn comes the closest. Though in my opinion it isn't quite as good looking. I don't know what other routes you own, but a less-similar route that shares some scenery characteristics I guess could be perhaps (some segments of) Dresden-Chemnitz*?
MSB as stated close. One or two of the US routes have a similar vibe - Sandpatch, Horseshoe Curve and Clinchfield. The Czech route arriving on Tuesday will be through hilly/wooded terrain.
Pfälzische Ludwigsbahn is a tale of two halves. From Mannheim to Neustadt it's very flat and open, but then you climb up and cross the Palatinate Forest to Kaiserslautern. Otherwise I would second Tharandter Rampe (Dresden-Chemnitz), but unfortunately that one as well as Ruhr Sieg Nord and Main-Spessart-Bahn are very old and look it.
Rhein-Ruhr Osten has fairly similar scenery given that it's just on the other side of Hagen. The route, like most of the other ones mentioned, is pretty old and offers different gameplay compared to Ruhr Sieg Nord.