A combination of two of the following would be the best options: ITV, Endemol Shine, RTL Group (Fremantle Media), Canal+ Group (Studio Canal),or Gaumont would be the best options. Preferable to do the latter three than the first two due to allowing more foreign properties in countries that Comcast, NBCUniversal, and Sky aren't major players in.
Those are good content options; though I wonder if Sky would be able to buy ITV now. Back in 2007, Sky was forced to sell off its stake in ITV because of competition issues. Have Netflix/Amazon Prime changed the UK market so much that Sky would be allowed to be under the same ownership as ITV now? I have some doubts given how much share of UK content production Sky and ITV have. Those two and BBC are basically like 60+% of UK content production...
Canal+ Group for French content, or RTL Group with all of its various TV holdings across Europe are pretty strong options.
I think though that Comcast may look hard at a cable deal with Vodafone. Why? Because Comcast built its cable business in the US by buying AT&T Broadband to become the #1 cable company across the US. There's a unique analogue there to how Comcast could build a "European Comcast" by combining Sky and Vodafone's cable unit.
Vodafone is the #1 cable operator across Europe (it accounts for around 35% of Vodafone's European operation), and while these days there's more of a so-called "fixed-mobile convergence" (so AT&T builds out fiber now and probably regrets selling AT&T Broadband in the first place), I think that a deal for Vodafone's cable unit is the most obvious outcome.
Also, Sky's weakest division by far is its German/Austrian division, which has been plagued by cord cutting causing steep discounting to the point where the division is basically running close to $0 profits. Sky has no cable operations in Germany/Austria or Italy or Spain, where it is a major PayTV provider. If Comcast were to get cable units across Germany/Italy/Spain, that would basically enable it to easily cross-sell Sky Now TV (Sky's OTT operation) as well as shift its satellite customers in Germany/Austria/Italy over to IPTV (internet protocol TV) from satellite.
What better way to build a "European Comcast" than to copy the same playbook that built the current US Comcast?
Of course, there's 2 issues: 1) cost, and 2) willingness on the part of Vodafone. Cost of some kind of deal would probably be around $30 billion cash + $20 billion debt assumption, for a total of around $50 billion (i.e. similar to what Comcast is paying for Sky: $38.8 billion with $10.3 billion debt assumption).
The bigger question I guess is willingness, these days AT&T has been building out fiber and probably regrets selling off AT&T Broadband because of the backhaul usage of fiber/cable.
I do think though that Comcast will make an approach to Vodafone for its European cable operations; Brian Roberts has always been aggressive about buying cable units where available, and Vodafone's are at least worth an approach given they would secure Sky's German/Italian operations.