No review needed for Sopranos. Probably the best TV series of all time along with Breaking Bad in my opinion.
Vikings is a pretty good show as well. Acting is usually good. The supporting cast for the most part is excellent. Floki and Rollo in particular are great characters. Some characters are really annoying like the Princess of France who has the most horrific fake accent I've ever heard. It can get cheesy at times like most other fiction TV shows but it is pretty high quality overall. I wish it focused more on Floki and Rollo in particular rather than just Ragnar most of the time although they do a much better job of that in the third season.
The action scenes are some of the best I've seen on TV. Not quite Game of Thrones episode 9 quality but close.
Plot is very simple. The show often struggles when it tries to be too dramatic. I'd like it much better if it took a more historical approach and cut out some of the unnecessary drama.
The costume design, screenplay and overall feel of the show is fantastic. It creates a wonderful atmosphere.
The show is pretty violent and there are some gruesome scenes. Again, not quite as gruesome as GOT but still pretty violent compared to most of whats out there.
Overall, I recommend it. It's pretty solid. It's certainly not HBO, AMC of FX quality but better than most of what's out there. That trailer for season 4 looks fantastic as well and now that the groundwork has been laid out in the previous seasons, I think the show will only get better.
That being said, there are better shows out there like Sopranos, the Wire, GOT, Breaking Bad, DareDevil, Hannibal, Hell on Wheels (Season 4 is awful though), True Detective...