I believe any food outlet in Singapore is good because it is a well accepted practice to eat-out/buy-home. Many families choose not to cook at home. As long as the food is average and above, there will be customers. The operator just has to decide which market to target - High-end? Low cost? Ethnic? Fast-food? The main concern will be overcoming the rental, which can be quite astronomical!
Cheers!
Your landlord decides how much you can earn, and you will earn. It's like taxi operators. They will monitor your earnings, and if they know you're earning above their predefined range, they will raise the rental and keep your earnings in check, and their profits unchecked.
It's not wise to rent a stall from Kopitiam or Koufu because you can't build your own brand. If you sell fantastic carrot cake, you will only be known as that carrot cake stall in Tampines Mall or Northpoint Kopitiam. As long as you're unable to build your own brand name, the more successful you're the more you're tied to the landlord's brand or the location. And to repeat, your earnings will be monitored and restrained. Your landlord will have you by your balls.
Don't judge a stall by the queue. One bad day with few customers is more than enough to wipe out profits accumulated over 3 good days. What's more, food is perishable. You need to run a big freezer for 24 hours, and it's like having an aircon switched on 24 hours a day for the whole year. Guess what ? Your landlord is not paying for your electricity bills.
You will be better off running your own stall in a old shop house, and if you've managed to build your own brand over the years, when you move your brand moves with you. As long as you have a website, your customers will know where to find you. More importantly, you can start running franchise.
When you have a good brand, you have your landlord by his balls, not the other way round.