I was thinking about this the other day and i feel that Thor Ragnarok could very well be as good of a film(or even better) as the first GOTG which i love and is one of my favorites MCU movies. It's without a doubt a tall order and something very hard to accomplish but i see plenty of potential and margin for that to become a reality. In terms of impact in the MCU i have little to no doubt that it will have a massive impact as GOTG had but in terms of a parallel in overall quality here is my reasoning.
The things i appreciated most about GOTG were the characters, the chemistry between them, the world building, the story, the use and choice of music, the humor and the heart of it all. They had also James Gunn which hadn't directed much previously. Now when i look at Thor Ragnarok i see a lot of the same traits.
If i had to point some small things GOTG was lacking a bit i would say the villain which was ok but nothing special, maybe the action wasn't much and the ending was good but it certainly could have been better too. These are things that TR seems to have a pretty solid hold on, Cate Blanchett's Hela looks to be the best MCU villain yet and knowing that we have Loki there too... Way more action and certainly there is going to be plenty memorable sequences. The ending at this point is everyone's guess but from the IW footage things will definitely end up with a bang. Then again not saying TR is gonna hit all the other highs GOTG did but some of the "lows" seems to be pretty well covered so it's a question of being able to deliver in the other fronts. Let's wait and see if it does.
No movie is really perfect but some like GOTG are very good and i expect fully TR to be one of those movies. One of the best in the MCU.