Simlish

Simlish is the language of the Sims. Some say it may be a mixture of Ukrainian and Tagalog, but this has not been confirmed. It might be possible to understand by studying the Sims' speech in certain situations. There isn't an official Simlish dictionary, but a good dictionary is found here. It is assumed that Simlish is the official language of SimNation.

SimCopter
SimCopter is the first game where they speak Simlish.

The Sims
This, having a lot more than SimCopter, was also a lot clearer. Common phrases "ralalalalib bubaya" and "o frazinnratt"

The Sims 2
The Sims 2 comes with better heard and newer phrases like "e wam". Common phrases are now "dej dej" and "ackabunad"

The Sims 3
The Sims 3 has the most. Common words are "teg teg", "hubble herni", "etne condoroley" and "zwitz zorg".