My personal rankings:
1. Morimoto Asia (widest selection of fish; don't go by what is listed online and sit upstairs at the sushi bar)
2. Kimonos (tradtional, consistent, not overpriced)
3. California Grill (good, but limited selection of fish; even more expensive than Morimoto!)
4. Tokyo Dining - Epcot (great service and view; limited selection, but decent quality, OK prices for where it is)
5. Kona Island (overpriced, limited selection, noisy hotel lobby ambiance)
6. Quick service locations (hard pass)
Haven't had sushi at Splitsville, so I can't rank it.