I'll only rate in relation between the games and myself, not gonna judge it on popularity or overal market/cultural relevance.

A D,i think. I liked animal crossing but i never was a super fan of the games in the series, i just like them fine. The mario 3d collection and Xenoblade DE are some games i really enjoyed, but i didnt played them for too long because i had done so before. The exception is Mario sunshine, which actually made me very happy.

I do not care for paper mario or the upcoming Age of calamity(if you count that as first party), so they dont really change anything for me. Idk if i'm missing something else that's coming out, but i think there's that.

2008 Wii was a drought year?

I count 4 important games:
MKWii, SSBB, Wii Fit, Animal Crossing City Folk.

2 Less important:
Wario land Shake It, Wii Music

Then 2 decent region specific games depending on where you are:
In America there was Endless Ocean & Mario Super Sluggers
In Europe there was Fire Emblem, Batallion Wars, , Donkey Kong Barrel Blast, DisasterDoC & Wii Chess

I really don't care about Animal Crossing, so my top game for the year was Paper Mario, but that wasn't enough. Fortunately, Age of Calamity is coming to save the year, but even so, it's been a week year.

While I haven't played Age of Calamity yet, it'll be a tall order for it to top Mario Kart Wii in my books, which means I'd actually likely put Wii's 2008 above Switch's 2020 in first party only.

Including third party it becomes closer; Ori, Immortals, Sniper Elite 4, Outer Worlds, Hotshot Racing vs World of Goo, COD World at War, de Blob, No More Heroes. Will have to wait til I've played all the Switch's releases for the year before I call an overall winner.

Honestly, for me, Age of Calamity pushed it into A territory. Even without taking the pandemic into consideration, it is still a solid year, and IMO, on par with 2018 (which wasn't a terrible year, just not as outstanding as 2017 or 2019).

D

Animal Crossing was fine, but I actually liked it a bit less than New Leaf. Mario 3D All Stars contains 3 great games, but is a lazy collection. Xenoblade Chronicles is still great, but most of the content is stuff I already played.

A new warriors game doesn't interest me all that much. Maybe it will be a pleasant surprise, but not enough to salvage the year.

But hey, stuff happens, and it's been a rough year all around. Hopefully things will get more back to normal and 2021 will be better.

Hyrule Warriors looks a nice story for a lame gameplay

I'm ready to watch all cut-scenes for free on Youtube

I really feel aside from MKDS. Every Mario Kart was shit post N64 until Mario Kart 8.  I got in 2008 for Wii was MK Wii..thought it sucked ass. Smash Brawl. Again sucked ass. Endless Ocean which was cool but short and Okami but already owned and played it on PS2. Tho I did get it again later on PS4. Now realizing NMH was 2008. I had 2007 in my head for some reason and deblob was fun but still kina meh year for new stuff to me on Wii. So 3 new experiences on Wii.  Rest were familiar.

PS3/360 I enjoyed more that year

DMC4

Eternal Sonata

Lost Odyssey

Macross Ace Frontier

Prince of Perisa

Valkriya Chronicles

Armored Core For Answer

I personally had a huge amount of fun with MKWii; I was a Uni student at the time and the multitude of 4-player splitscreen matches we had in our dorm room, usually with drinks, were some of my fondest memories of those years. I don't care for Smash so Brawl offered me nothing, but I thought World at War was a series best and World of Goo was an awesome surprise. Even had some decent fun with Boom Blox too.

A - 2017
B - 2018
B - 2019
C - 2020