It's hard to beat, or even compare to, the classic Christmas songs; Slade, Shaking Stevens, The Pogue & Kirsty McColl, Wizard etc. All thee, and many more, have stood the test of time and are still as popular now as ever before. There are a few more recent ones that I actually quite like:
Leona Lewis - One more Sleep
This has the Christmas feel - complete with jingling bells - and has a nice old time 'big' Christmas ballad type vibe.
Arianna Grande - Santa tell me
I like how this is Christmassy but has a modern pop vibe too. Slight Mariah Carey vibes in the chorus vocal