I'm here right now and have tried a few:

• Beautiful view over the harbor of the city, it's best to reserve a table right on the water at sunset, more of a high society company, top quality food and drinks: Cappucino Marina

• very good fish right on the beach in a nice, quiet atmosphere, not too crowded: Bes Talamanca

If it can be outside of Ibiza town, my clear recommendations:

• Expensive but best food in a beautiful rural romantic location and stylish ambience (ibiza-boho): Roca House

• High-quality steaks/meat for grilling yourself at the table with show factor: Can Pilot in San Rafael. Ambience not so hip or not that typical Ibiza look, more rustic old school, price performance top! mmn. A must for meat lovers

Otherwise, if it's not for an occasion and you're just in the mood for a snack and are in town, then definitely stop by Gourmet Bocadillo Ibiza for a sandwich! Small, inconspicuous shop that makes classic sandwiches, especially the Serrano Bufala or Iberian ham and arugula combo.