That's absolutely not comparable. EA had no choice than to announce a free DLC for ME3, after they totally [censored] up the end (plotholes, immediate end, starbrat and space magic, falsy promises that your choices matter at the end etc).
I wasn't always happy with Bethesda with all the bugs in Skyrim, but they do their best as it is extremely difficult to avoid bugs in such a HUGE game (that you can play in 1000 different ways) and regarding the fact, that many different xbox versions are out there.
Both sets of arguments don't fly.
EA releasing DLC for what is a creative choice.. doesn't make any sense.. (and in my opinion sounds like orchestrated marketing hype) also the ending doesn't influence the game as such. (it was a very vocal but numbers wise minority who demanded it..)
Bugs in a sandbox game are indeed somewhat unavoidable.. However there is a huge difference between game breaking bugs and glitches. Also the architecture for the 360s is the same, no matter what the model is.
Some bugs in Skyrim were avoidable and very specific to the engine and should/could have been ironed out before release..