Any kind of battle can be riveting, or extremely boring, or anything in between. You need a few things to make a battle interesting:
- Stakes. Not the physical ones (unless you're battling a vampire, then go for them), the story ones. The battle must be important to the characters. A schoolyard brawl vs a bully that's been hampering your child character for a while will be more interesting than the 20th fight against a dragon of your OP monster slaying character.
- Expectations. A good writer will let the readers know where on the power scale the participants in the fight are at the beginning. That's why litRPGs are so popular, they have an easily understandable power gauge.
- Dynamic action. Attacks, parries, evasion, counters, feints, etc... The characters need to adjust to the flow of battle, and to be active on their own.
- Terrain, surprises and other optional elements. Yes, a battle can be good without any unforeseen moves, clever use of the environment, exploitation of a participant weakness, psychology tricks or other story tropes. But done right, and in the right amount, these elements contribute greatly to the intensity of the battle.
All of those elements are not limited to fantasy battles, nor to physical battles between a few characters. You can have armies spar on a large battlefield, or courtesans face one another in a battle of wits, and if you apply the same ingredients as for a battle (Stakes, Expectations, Dynamic action and some optional elements), you'll have an interesting conflict!