What makes a good architectural design?

1. Technicality
First of all, no matter how the design looks like, the design must be feasible, detailed, and able to stand. Do note that technicality does not equal to practicality - the design may be technically possible, but some of the unnecessary materials can be removed when considering the cost/practicality of building the building.

2. Aesthetic design values
Once the technicality requirements are fulfilled, the next aspect would be the aesthetic aspect. It should be timely (suitable to the styles of that period of time). It should also be the designer's self-expression. Aesthetics is very subjective; thus the designer needs to consider the culture of the region and the context for building the building.

3. Social design values
The building might be feasible and look pretty, but if it does not serve the community in any way, there is no use in letting the design come to fruition. For example, the concept of having HDB flats in Singapore was to make public housing affordable, and it has successfully done so. Also, if a designer designs a building that can conserve energy, or be built in such a way that it can be more affordable for the homeless or for those in slums, that would add a social value to the building design.

4. Traditional design values
This value would apply according to who the building is designed for. For example, if the building was to be an Asian Museum, tradition would have to be considered when designing how the museum looks like.

5. Economic design value
This value would be very important when a designer is designing a building that needs to be mass-produced or be made affordable to the masses. The building should be simple and minimalistic, such that less materials would be used without compromising on quality, so that it would be sold for a cheaper price for the masses.

Source of inspiration: http://en.wikipedia.org/wiki/Architectural_design_values#Aesthetic_design_values
(Explanations and examples stated above are just my point of view, it's not based on the source.)