Ulysses does 5d2 + 10 ordinary damage and 9–12 Water damage, and adds 50 to your accuracy

I can't remember the stats for a Griffin bow, but an item "of Darkness" decreases your recovery time (i.e. the bow will shoot faster) and is vampiric (i.e. some of the damage it does is added to your hit points until you are fully healed).

A bow "of Carnage" casts a fireball when it hits. It is extremely useful at long range, but dangerous at short range because your party gets caught in the fireball's blast.

The Perfect Bow is the most inherently accurate bow in the game, doing 5d2 + 12 ordinary damage, but that's all it does. Retrieving it is also one of the Archer quests.

Ania Selving is probably the least useful. It does 4d2 +9 ordinary damage, adds 150 to your accuracy and 5 to your bow kill, but it drops your armour class by 25.

You didn't mention this, but I think there's an enchantment in that game called "of the Dragon". If so, it causes additional Fire damage, and protects you against fire, and is one of the best enchantments for weapons.

I would rank these in the order:
1. Ulysses
2. "of the Dragon"
3. "of Darkness"
4. The Perfect Bow
5. Ania Selving