What stats do traded Pokemon keep?

According to bulbapedia, trading affects friendship level differently for each generation of the game. I will outlay it in each generation below:

First Generation: Trading will reset to 0
Second Generation: Trading will reset to 70
Third Generation: Trading will reset it to base stats (usually 70 or 140, full list here)
Fourth Generation: Trading will reset it to base stats
Fifth Generation: Trading will reset it to base stats

Thus, no matter what generation the trade is completed in, a freshly traded Golbat will not evolve upon a level up.

Stats other than happiness, such as Effort Values (EVs) and Individual Values (IVs) will however, be preserved.