The early-planet-colony-rush is strategy independent and amounts to all-out-chaos in an attempt to grab powerful worlds. This is why some people have been advocating for more powerful "prime" worlds that could be built up over time. Currently, there is no benefit to focusing efforts on planetary development. The only focus is on gaining more planets. That's not to say that you don't develop your planets, but that it's secondary to colonization for every player.
Sid Meier's Civilization series approaches this problem through two very useful mechanisms. You need both workers and population for each city to be useful, and buildings are built over a much longer period of time. This means that a focus on building more workers means more tile improvements. More tile improvements means more food, which leads to more population, which increases workable tiles and allows the city to support more workers to build and maintain those tiles.
When you take all of these dynamic attributes together, any five older cities are worth more than ten new ones. This is because both strategies are rewarded. Someone who rushes out and builds 10 cities will typically be leaving several completely un-protected. Not only that, but builders can only focus on one tile at a time, at a single location. This means someone who builds workers, increases food for population growth, and focuses on strong city defense is often at an advantage early-mid game. Obviously the individual who colonized twice as many areas has twice the potential, but his resources are spread out too thin, leaving him vulnerable to attack, and stunting his early-game-growth. If he is both clever and lucky this can work to his advantage, but against a powerful and aggressive opponent he would be crushed unless he was able to find a diplomatic solution.
Why is Galactic Civilizations different? Population is treated as a universal variable instead of a local one. The purpose of population is mostly for the acquisition of wealth, which is then used to fund production. This means that the population of any planet can fund the production of another. If Civ5 used their population variable in a universal manner, then an increased population in your home city would allow you to work a new tile anywhere on the map, including one at a brand new city.
This wouldn't break all the mechanisms of Civ5 by itself, but if you combine this problem with a second variable, "production" you start to have a lot of problems. Production, in terms of city growth, can only be accomplished by workers. They have to be built in order for a city to grow, and they can only work a single location at a time. You have to decide between building a settler and colonizing a location, or building a worker and focusing on growth. Since "production" is mostly a universal variable in GC, you can work a single tile at every colony simultaneously while also building colonizers.
So imagine Civ5, where an increase in population at any city allows you to build on a tile anywhere, and you do not need any workers. Instead you work on a single improvement at each city simultaneously, and this is also independent from unit and building production. There would be no reason not to run out and colonize every conceivable location. Couple this with the fact that most cities can only build five-ten buildings, and it's nothing but a mad-rush at land grabbing.
Since there are so many colonizable locations in GC, having production set up as a mostly universal variable makes sense. Workers would just be an added annoyance. However, population is too powerful in its ability to affect universal production. There needs to be a mechanism put in place to limit this effect on a per-planet-basis. I would suggest planets that have to fund their own production, but this would most likely be met with strong criticism from veteran game players as it has been a core game mechanic since the beginning.
At the moment, my suggestion is for developers to focus on more powerful planets that allow you to develop "prime" worlds over time. However, I do feel these other issues also require some consideration.