Frankly, Southampton is a very, very bad places for restaurants. Always has been. Some of those listed are amongst the better ones, but there simply aren't that many that are truly interesting. Some present their food in a posh way and people think it's great as a result, but there's nothing worth getting excited about. Some of the better food is actually in the places that look ****e. Miguels used to be pretty good, funny little place by the station. Not much to look at, often empty, but a few years back they did very genuine, good Spanish food. There's also a place in St Marys that does good Afghan etc food, apparently.
And if you're a veggie, screw it here. Just get the train to Brighton and go to Terre a Terre. Failing that, try Demuth's in bath. Both top notch.