The research looked at 20 cruise companies, asking thousands of passengers to rate them across 11 categories.
Viking received five star ratings for all categories which included customer service, passenger-to-space ratio, onboard facilities, cabins, food and drink, port excursions, social atmosphere and value for money.
The other companies to round out the top five spots were Saga Ocean Cruises, Azamara, Hurtigruten and Silversea.
But bringing up the rear - at the very bottom of the league - was MSC Cruises, with a customer rating of just 57 per cent. The Which? Survey revealed MSC had been given two-star ratings for most categories. Of the 20 cruise ships surveyed, MSC also had the lowest rating for "description matching reality".
Royal caribbean, Norwegian, Cruise and Maritime and Holland America were also among the bottom of the heap.
All-inclusive cruises, such as those with Viking, may have a higher price tag, but there generally aren't any surprise fees.
For discount cruise deals, excursions and drinks can all add up, leaving some passengers with a higher bill than if they'd gone for the all-inclusive price tag in the beginning.
Which? Travel editor Rory Boland said cruises shouldn't be about long queues, expensive extras and rubbish excursions:
"Bargain headline prices often mean dubious add-ons once you set sail," he said. "A far better experience was had by those who paid for an all-inclusive cruise, where pricier upfront tickets will give you peace of mind and might actually leave you paying less overall."
The fewer, the better fare
The top-rated cruise ship company in the survey, Viking, carries a maximum of 930 passengers per trip, compared to the largest of MSC ships which carry more than 6000 passengers.
Which? Cruises shouldn't be about 'long queues, expensive extras and rubbish excursions' . Photo / Damon ORoad, Unsplash
And when you're staying in one place for any length of time, personal space becomes a precious commodity.
Passengers onboard MSC complained about congestion and having to wait in queues for restaurants and entertainment.
P&O was given a low rating for its social atmosphere, with some saying the pool area was "overrun" and "a nightmare".
Which? said Viking's more upmarket ships mean passengers can avoid crowded bars and casinos which tend to be synonymous with cheaper rivals.
Passengers still happy with MSC
A spokesperson for MSC Cruises told MailOnline Travel they were disappointed in the survey results.
"However, we are sure that the small sample size of 67 passengers is not representative of our overall passenger experience given that in the UK market alone we have seen a 37 per cent increase in passengers from 2018 to 2019, with a high number of repeat guests."
"After every cruise, we contact guests for feedback and as a result, create an overall satisfaction score, which is not in line with the Which? findings. In addition, MSC Cruises is an award-winning cruise line, and in 2019 alone we collected over 50 awards around the world recognising the strength of our product."
