Is there any animal that has a better sense of smell than a dog?

The keenest sense of smell in the insect world, and in fact in all nature, belongs to the male silkworm moth.

This valuable moth uses its two antennae mainly to locate the female and can detect her signal, or smell, up to 6.8 miles away, amazing for an insect only about 1 inch long!

Fish have a well-developed sense of smell, even though they inhabit an aquatic environment. Salmon utilize their sense of smell to identify and return to their home stream waters. Catfish use their sense of smell to identify other individual catfish and to maintain a social hierarchy. Many fishes use the sense of smell to identify mating partners or to alert to the presence of food.

http://www.bigsiteofamazingfacts.com/who-is-the-best-smeller-in-the-insect-world

https://en.wikipedia.org/wiki/Olfaction#Olfaction_in_non-human_animals

There are a multitude of answers among which we find:

Same family: WOLF -- One of nature's most intelligent and the animal with the keenest sense of smell of any mammal on earth.

https://wolfhaven.org/wp-content/uploads/2016/03/optional-education-handouts-reduced-size.pdf

Polar bears are known to have the keenest sense of smell of any mammal and have been known to pick up the scent of a seal from a distance of more than five miles and to track it down.

http://seakayaking.wordpress.com/page/2/

In fact, it is speculated that the Turkey vulture has the keenest sense of smell of all animals.

http://www.kern.audubon.org/tvfacts.htm

keenest sense of smell: kiwis

http://www.rainbowsprings.co.nz/kiwi-conservation/kiwi-facts/

I think the Bloodhound is # 1.

https://en.wikipedia.org/wiki/Bloodhound

BEAR: Although the region of the brain devoted to the sense of smell is average in size, the area of nasal mucous membrane in a bear's head is one hundred times larger than in a human's. This gives a bear a sense of smell that is 7 times greater than a bloodhound's. In addition, they have an organ called a Jacobson's organ, in the roof of the mouth, that further enhances their sense of smell.

https://animals.mom.com/creature-sense-smell-3339.html