It's always that the grass is greener on the other side of the fence..

The UA flights I've taken, food has been solid. Not outstanding, but better than DL. They do run out of snacks though, like you can only have one bag of chips, you can't take two...then just one was left over and I could get the second one after all when the FA came back up to the front.

AA has generally been the best in the food department.

The general trend though is that for most airlines food quality is decreasing. KE used to be good, now is really poor. CI is mediocre through outright bad. AY is getting worse. TG is also pretty bland now. CA is the only airline with good selection and food at the moment, at least of the ones I've flown.