These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Van Halen
Broken Base: Dave vs. Sammy. Doesn't help that the band changed its style in the latter period.
Covered Up: Many of their covers are better known than the originals; regarding "You Really Got Me", Ray Davies himself said that it sounds better than his band's own version (the original, mind).
Dork Age: The Hagar stuff for some; whoever came after Hagar for most.
Enters Canon Discontinuity, as the band released a compilation with songs by both Sammy and David, but not the third guy.
Gary Cherone, for his part, was gracious enough to not speak out about any of this (including his non-inclusion in the Rock & Roll Hall of Fame induction). Considering the way he was treated by the band during his tenure with them, he had every right to.
Epic Riff: "Panama", "Jump", "Hot for Teacher", "Runnin' with the Devil"...
HSQ: Spread across all of their music, it's somewhere in the hundreds, maybe even the thousands. Don't forget what's on the blackboard in the "Hot For Teacher" music video.
Hype Backlash: Gary Cherone was hyped as having "a voice like Sammy Hagar and the stage presence of David Lee Roth." The poor guy was doomed from the start.
Pretty much. The real headache with Cherone is that he was never a literal or vocal fit to begin with. Look at the two music videos they did, "Fire In The Hole" and "Without You"; it's clear he was in much better shape than the rest of the band (but in their defense, each original band member at the time was/is 7-8 years older than Cherone). When he joined Van Halen, he altered his delivery to try to match the band's well-known sound, instead of singing at his previously known register with Extreme. If he had tried to sing the way he normally does, Van Halen may have been a much different band with him.
Mis-blamed: Eddie was already shifting the band's sound when Sammy came in. Part of the misblame is arguably due to Dave's opposition to said shifting.
Similarly, Gary Cherone is usually blamed for Van Halen III's status as being terrible despite arguably being the best actual singer the band has ever had. They also brought back the DLR-era songs in their setlist, which were largely absent during the Hagar era.
Wolfgang Van Halen is regarded as an inferior bassist to Michael Anthony as well, though this can boil down to fans still being bitter on Michael being forced out for no clear reason.
Sampled Up: You might not know "Jamie's Cryin'", but is probable you've heard Tone Loc's "Wild Thing".
Signature Song: "Ain't Talkin' 'bout Love", "Runnin' With the Devil", "Jump", "Panama", "Hot for Teacher".
They Changed It, Now It Sucks: Dave left the band in 1985 because Eddie wanted to change their style. With Dave out of the way, Eddie did just that, incurring the wrath of fans who slammed the band for "not being fun anymore".
Vindicated by History: Three albums were not well-received at the time of release, but now they are looked upon with somewhat kinder eyes. Songs from Roth-era Fair Warning are still played on the radio today. 5150 was Hagar's first, which caused the Broken Base, but now both camps tend to admit the other had some good material. And then, the still-divisive Van Halen III is now getting some positive recognition from people who actually took the time to listen to the songs.
He was off illicit drugs. He did clean up once to record "Jamie's Cryin'", but... well, The Other Wiki speaks for itself:
For recording of the song vocalist David Lee Roth wanted to go for a cleaner, "poppier" sound and quit smoking and drinking for a week before the final version was to be recorded. The band noticed the difference and Ted Templeman ordered him outside to smoke a cigarette. He smoked one, and drank half a bottle of whiskey, returning half an hour later and recording the track.
Yoko Oh No: According to an LA Weekly article, Valerie Bertinelli is to blame for causing tension within the band that ultimately resulted in Roth's dismissal.