SG1 didn't need to gift the aliens with English. It only needed to establish that everyone we hear as speaking English offworld is really speaking Go'a'uld, just like we hear English when, say, Nazis in a WWII action flick are speaking German. The ones who don't speak Go'a'uld need translating. Throw in an occasional remark about Daniel talking just as fast in either language or Jack not immediately understanding English when he comes back until he's got his coffee, and you're done. For Atlantis, sub modern Ancient (nice oxymoron!)
For the first few seasons of SG-1 (indeed, for the majority of the show), it was possible to handwave the language problem without much suspension of disbelief. The inhabitants of Abydos speak English where they didn't in the movie? No problem-- Daniel obviously taught them in the interim. The Abydonians are shown to worship everything he did, so this is quite reasonable.
All encounters with the Goa'uld, Jaffa, or Goa'uld-occupied worlds: They're speaking Goa'uld, the same language spoken on Abydos. Daniel and Teal'c are fluent in it, and Jack can get by due to his experience from the original mission. Sam is the only character that requires an explanation, and it's reasonable that she's cramming the language offscreen. (Later, the Goa'uld come to the SGC and talk to folks like General Hammond, but this takes place late enough that he should have had enough time to learn it.)
"Cold Lazarus", "Fire and Water", "Tin Man", "Enigma" and "The Nox" all feature aliens or technologies that could theoretically learn English in a hurry and get around the language problem. "Emancipation" is about the only S1 episode where the culture had no obvious reason to understand either English or the Goa'uld language. But the less said about that ep, the better.
S2 is roughly the same, "The Gamekeeper", "Message in a Bottle", "Spirits", "The Fifth Race", and "Show and Tell" all having handwave technology/aliens, and the majority of others dealing directly with the Goa'uld or Jaffa again. However, there are three anomalous episodes, these being "Prisoners", "Touchstone", and possibly "Holiday", where the cultures or people in question cannot reasonably know English. This is where it takes a downturn, if three episodes are too much to overlook.
S3 continues this trend. In "Learning Curve", since we don't actually see first contact with the Orbanians, there might have been enough time to exchange languages. Ditto with "A Hundred Days." (To be fair, the same was true in S2 with "Touchstone".) But along with these iffy ones, there are several real anomalies: "Past and Present" and "New Ground." And probably "Demons".
For the next few seasons, the pattern is the same. 1-3 anomalous episodes where the characters really shouldn't be able to speak upon first contact, and 1-3 episodes where we don't actually see first contact, so it's possible to explain it away. That number of episodes is annoying, but it's not as bad as it could have been.
In the last few seasons, the incidents actually get fewer, primarily because the characters don't explore many new worlds.
Now, with the advent of Atlantis, none of these explanations work anymore, and we're stuck with "the gate did it." That really is a pet peeve.
