You'll have to draw your own conclusions, because my experiences have been in Y and not C.

Quick summary of my experiences (Note that UA offered an 'Asian Vegetarian meal'. You'll be stretching your imagination a bit to find the 'Asian' bits
UA 893 SFO-ICN - ugh
UA 853 SFO-NRT - blah
UA 837 SFO-NRT - blah
UA 838 NRT-SFO - very good, and a proper Indian meal (because this flight comes from SIN and there are a lot of Indians connecting to the West Coast on this flight)

If you are very picky, I'd recommend Asiana, Korean or SQ. Korean and SQ have a specific 'Hindu Vegetarian meal', and Asiana's meal is based on Indian cuisine.