Interesting, I've always preferred Kinnect to Wii

As a engineer Kinect allowed some dope things with computer vision that was not common before. Wii motion controls in other hand were useless tec with many years old

This question feels a little misguided: Why are comparing a single showcase event to an entire several-year-long period? Maybe a better question would be whether the late-Wii/early-Wii U years were better or worse than the Kinect years…at which point — though not being too greatly informed the Kinect period of gaming — I would prolly have to say Kinect had it worse. The reason being that Microsoft went from the console manufacturer who, against all odds, finally caught up to Sony…to all the sudden being the company looking to replicate the success of NWii, which would serve as “the beginning of the end” for the Xbox brand as the years which would follow this would lack any new and exciting first-party experiences.

As you said, Nintendo's E3 2008 was just one bad presentation, while Microsoft tried to force Kinect on the consumers for more years...

Btw, I live in Natal, the city which project Natal was named after. =)

If we're comparing one Nintendo season/press conference compared to several Xbox conferences, Xbox is worse.
If we're comparing 2008-2013 Nintendo to 2008-2013 Xbox, then Xbox had better third-party games and hardware, but Nintendo had better first-party offerings.

For me? Nothing will ever out-cringe that Wii Music presentation. Nothing. Ever. lol

A single E3 is not an era.

Wii is better than Kinect. Wii had a ton of shovelware sure. But it will had Mario Galaxy. Xenoblade. The Last Story. Pandora's Tower. Earth Seeker. Captain Rainbow. No More Heroes. Madworld. Zak & Wiki. Tatsunoko vs Capcom. de blob. Metroid prime 3. Fragile Dream.s  A boy and his blob. Endless ocean. Kirby Epic Yarn. DKC Returns. Etc etc etc. While Wii did lead into Wii U. Wii U still had some great exclusives and Nintendo bounced back with Switch.

The fuck did Kinect have? Just crap. It also marked the beginning of a brand's downfall. From Kinect to bad leadership Xbox has never recovered.

As for conferences. Nintendo 2008 is bad. 360 2009 was ok but a lot of the cliche dumb shit of the era. 2010 on was a disaster. Wii had an amazing E3 in 2010.  An average one for their time in 2009. 2011/12 sucked. But again by 2014, they had a good one with Wii U. Xbox continued to have no memorable conferences in the XBO era until maybe 2018. By that point, Nintendo was in full Direct mode and knocking out good ones all the time in general.

The Wii had a relative dud year following E3 2008, but audiences had just gotten biog entries in most of Nintendo's biggest franchises over the prior 18 months, and things were looking up within a year. It was a bad year, but not unparalleled. 2003 and 2016 come to mind.

The Kinect era featured Xbox trying to completely rebuild itself around a peripheral, crippling the brand to the extent where it has never recovered. Various studios were created or revamped to create Kinect games, and at least a dozen retail Kinect-only games and twice as many digital titles were released by Microsoft from 2010 to 2014. When the X1 was released, the forced inclusion of Kinect added $100 to the price and gave the PS4 an instant advantage. This is not counting the various other games that had to spend time adding Kinect support instead of other features.

E3 2008 hurt the Wii. Kinect crippled the Xbox brand.

As someone who had Kinect. That one is worse. At least Nintendo still uses motion controls. Forced Kinect at launch is one of the reasons Xbox One didn't do that well. 

Yes and yes. On the first-party front, Nintendo had a disproportionately heavy pre-E3 lineup for Wii in 2008.

Super Smash Bros. Brawl and especially Mario Kart Wii were huge. Wii Fit (which had released in Japan in December 2007 and other regions before E3 in 2008) may have been almost exclusively for casuals or nongamers, but it sold like crazy. 

After that, I think it was just Wii Music, Wario Land, Mario Super Sluggers, and Animal Crossing in global releases. Only Animal Crossing had another installment after 2008 of those IPs. Animal Crossing: City Folk was viewed as playing it safe compared to the previous entries and sold much less than Wild World did on DS. New Leaf would even end up selling better despite 3DS having a lower hardware total than Wii. 

On Wii, 2009 was also quiet until around May-June (the inverse of 2008). After Wii had such a strong first-party lineup from November 2006-April 2008, it seemed to go on a break from May 2008-until around May or June 2009 (Punch-Out or Wii Sports Resort as the return to form, if you will). 

There were obviously third-party games on Wii to enjoy, but it doesn't instill confidence for a console that was still selling like hotcakes to have pretty much an entire year in a row that was quiet in first-party games after about a year-and-a-half of notable releases.

In all fairness, Switch had a very strong 2017 (March-December) in first-party titles, while it took until about October-November 2018 for the Nintendo software to pick up again. 

Some of the philosophies of Wii and E3 2008 did end up hurting Wii and Wii U. But Switch is a meteoric success. 

Kinect as you said ended up crippling Xbox. Xbox has still never fully recovered from the Xbox 360 to Xbox One transition (where Kinect was pushed big time for Xbox One and initially bundled which raised the price) and Xbox is now just one part of a more successful Microsoft Gaming division. Some employees even said it's tough to think of it as Xbox, it's Microsoft Gaming. 

One other thing I will mention in this long post is PlayStation. E3 2006 was a fail on the PS3 front. PS3 struggled until the Slim revision in the second half of 2009. Sony was very arrogant, packing a ton of tech into PS3 at a high price. PlayStation has recovered from those early days of PS3 (they already did late in the PS3's life, or at least by the early life of PS4) but a lot of damage was done.