It depends on the criteria you are using. I mean decidedly 'less than excellent' on welfare terms, in my opinion. If you mean do they have an excellent collection, or excellent breeding record, then I wouldn't disupute that. In fact, managing exotic ungulates in a way not dissimilar to domestic farm stock can be a very effective way to breed from them. For years the huge population of collared peccary at Flamingoland, when most zoos were breeding them very infrequently, was down to the fact one of their main keepers was an ex pig farmer. Similarly, a number of the hoofstock keepers at howletts and port lympne come from domestic livestock backgrounds. I'm sure this is the case for many collections.
But on welfare terms, I would say they are most definitely not in the 'top 5'. What I've seen is mirrored on a number of threads already on this forum, so I won't go into it to repeat what other's have said, but you should really visit the place on a cold winters day to see what most visitors, who come during the summer, don't. Some parts of the zoo are great, and they do really well with a few species that other zoos don't seem to manage to establish. But I think its precisely becuase they have the space and the facilities it is baffling to see some animals given vast enclosures while others make do with extremely small spaces.