Platinum may be my favorite Pokemon game ever, so I say Sinnoh is top 2 region of them all tbh (Hoenn being the only other one I consider more or less on par) --- 30 years of Dragon Ball! DBZ, Shonen, Metal Gear, Spurs
Sinnoh had its problems (slowness, HMs abuse, hindering terrain), but was really diverse. Unova was too straightforward, but had some character to it and thankfully pulled back on the HMs. Kalos was rather meh to me overall.