Well of course Halo would appeal to Nintendo fans more. Hardy LeBel - Halo: Combat Evolved's lead multiplayer designer - has gone on record saying that the whole point of CE's multiplayer was to make a fun party game that happened to be a shooter; "a shooter Nintendo would have been proud to release."
Answering the question at hand though, I'm taking Halo. I think the best Call of Duty campaigns (World At War, Black Ops, Black Ops 2, etc.) are up there with the original Halo trilogy, but Halo's multiplayer is better imo. I personally prefer Halo's more arena shooter-inspired roots with its weapons and equipment on the ground, as I think it lends itself to a more dynamic experience. (Not to mention the vehicles!) Map control is a very important part of Halo, in a way that I feel Call of Duty kinda lacks. That same focus is actually why I gravitated to Splatoon so much once Halo went down the gutter post-Halo 4! The Halo games tended to age better too, I feel. Halo: Reach feels better to play than Black Ops 2 does, for example. The gunplay still feels good, though not as snappy as later Halo games or Bungie's Destiny, but it doesn't feel...
old like similar aged Call of Duty games tend to. I think this may come down to Bungie's (and yes, even 343's) excellence in game feel and gunplay more than anything; popping a headshot in Halo or Destiny feels satisfying in a way very few shooters do. And if we're talking art style, even Reach's gritter art style compared to the other Halos still has a bit of a "pop" to it VS CoD's more realistic style. Holds true even when compared to more colorful maps like BO2's Nuketown 2025.
Halo: Reach - Highlands (those skyboxes <3)
Black Ops II - Nuketown 2025
I think what really takes Halo over the top though is Forge. Having a map and game type editor takes things way further than anything possible in CoD. The game types and maps people made really embodied the "party game" ethos of the original Halo's multiplayer. Dumb mini games like Halo's version of Jenga, a recreation of Duck Hunt, among other wholly unique experiences like Speed Halo and Trash Compactor were stupid fun. And when you got tired of all that, you could still hop into ranked and get your sweaty competitive experience, hop into some stellar singleplayer campaigns, or mess around in the PvE Firefight mode.