I think that it's difficult to find a place where you would have a bad feed here. Though some places are definitely better than others. There is such a huge range of cuisines and, in the main, many restaurants supplying each of them, that the choices are endless. I have eaten at only a small percentage of the restaurants on this island and these are my favourites:

Thai Food: Tho's Restaurant at Thalang located just south of the traffic lights near the Honda dealer - Every dish is just superb.

Mr. Tu's Restaurant in Patong (excellent Pad Thai). Located towards the south end of Patong just past Phuket Directory on the opposite side of the road. You can have your laundry done there too.

Da's Restaurant  next to the Two Black Sheep on Rat-U-Thit Road, has a well deserved reputation and is a very popular eatery;

 Dang's Restaurant  next to Number 6 on Rat-U-Thit Road in Patong serves delicious meals for westerners and Thais, as proven by the difficulty of securing a table there at meal times.

 Kata Mamas at the South end of Kata Yai Beach has very good food and the location is very hard to beat. The Rasta Bar next door is a great place for a drink.

 Kalasin City at Mae Ubon Market on Nanai Road (second in from the road) serves delicious food. Gravy noodles with chicken is especially recommended.

 Pan Yaah Restaurant at Kalim Bay (around Kalim Bay opposite the construction on the hill); is more upmarket and has spectacular views across Patong Bay. For the romantics.

  Cherng Long Thai B B Q near Central Festival is a great place for a night out. 98 Baht for a cook yourself barbeque buffet.

 Lotus Restaurant at Bang Thao Beach behind Laguna is located right on the beach. has a great menu and delicious food.

 Godzilla's in front of Super Cheap in Phuket Town has great Thai food and you really won't believe the prices. Buy some food and you can order a jug of beer for 15 Baht.

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Western Food:

Molly Malones on the beach road and Scruffy Murphys in Bangla Road. These Irish theme bars serve big portions of excellent food. The Guiness and Beef Pie is superb.

Surin Bay Inn has great food and, in my opinion, the best breakfast on the Island. Worth the trip up the coast to Surin Beach to give it a try.

The Tavern on the Hill, located on Ha Sib Pee Road, has great Sunday roasts. Beef, pork and lamb with the necessary sauces, served with great vegies.

The Bar B Q Hut in Patong is the place to go for Mexican food and a good breakfast. You can find it on the southern end of Rat-U-Thit Road. If you're heading south it's on your left. 

 Don's Place, down near Nai Harn Beach, serves a great selection of good food, both Western and Thai.

Indian Restaurants: I don't particularly frequent Indian Restaurants although I won't say no to some Nan bread and Hummus. While I haven't had Indian food for quite a while, I have eaten at the Dubai Restaurant on quite a few occasions and I'll go back there for my next Indian feed. They have three locations. One in the vicinity of Christin Massage on Rat-U-Thit Road, another opposite Patong Bayview resort on Rat-U-Thit Road just north of the Sainamyen Road intersection, and one on the southern side of Beach Road near the soccer fields.

Japanese Restaurants: I'm not a great fan of Japanese food although I eat it in Japan. While I haven't eaten at either the Sumo Restaurant or the Zen Restaurant, both in Patong,  they seem to be quite popular. I have eaten at the Oishi buffet in the Index Living Mall near Big C a couple of times, and would certainly recommend the food there.  

Italian Restaurants: There's at least one on every block. The best one however is quite a drive for me. It's the Rum Jungle Restaurant opposite the Ayudhya Bank at 69/8 Baan Suan Road in the Rawai - Nai Harn area. Tony and Jo really know how to prepare the best authentic Italian cuisine and their Thai dishes are excellent also. Well worth the drive.