Netflix is one of those few online video platforms which can challenge Google's YouTube

In order to successfully challenge Google's seemingly-insurmountable YouTube, at least the following three qualities are needed:

• Massive technology infrastructure to upload, transcode, search and stream user-generated videos.
• Large user base running into tens of millions, which is interested in watching movies/videos.
• A popular brand name.

I strongly feel that among the few contenders that seem to have the ability to successfully mount a challenge to YouTube, Netflix has a prominent position. Its technological infrastructure and capabilities cannot be questioned, considering its existing business. Equally importantly, it has a massive, paying customer base, and this customer base can be used to both upload user-generated videos [like YouTube] and to watch these same videos [either supported by ads or included alongside the customer's premium Netflix streaming subscription package].

Update [9-Jun-17]: Amazon [especially], Facebook [especially], and also Microsoft can mount a challenge to YouTube.