My first MTB back in the '90s was a Diamondback Sorento with an upgrade Rockshock that I bought from the LBS. So I guess that they were "good" back then.
But then I stared seeing the in Box Stores so I guess that they weren't so good any more.
Now I'm seeing them on the internet in the hands of "good" riders but still at Dicks. So.....
If I'm in the market for a Trek or Giant should I be looking at Diamondback too? And if so, what year did they stop sucking and get back to making good bikes?
I'm looking for a hardtail, Currently considering a Marlin 7 or a Talon 1

and how come Cannonale fell off the radar? Those were sick bikes back "in the day".

Diamondback brought out a pretty decent bike in 2016/17 called the Release, and a few variants of it (Catch, Clutch, Release 29, carbon frame). It’s good. It has an excellent linkage. Compared to MY23 bikes appearing now it’s getting out of date.

Sometimes it has been an excellent value. They had a corporate reward discount and the password was an open secret. The bottom spec version they sold via Performance/Nashbar in 2017/18 was a screaming unbeatable deal when it went on clearance. You can get a discount now through IMBA, I think.

They have a good hardtail called Sync’r. They brought out a new enduro model called Mission but I have heard little about it.

They have a new short travel bike in the pipeline but it’s Covid-delayed. Going down the rabbit hole on that I learned that the guy running the company really believes in the Atroz as a low price entry level bike although few people now give it the time of day due to its very basic suspension design.

Eric Porter, who you can find on YouTube, rides Diamondback. So did Seth of Berm Peak though that recently dissolved for reasons unstated. I think Porter is an actual employee, or at least more directly involved with the company bike development, where Seth was sponsored.

Cannondale brought out a new Jekyll last year, FSR with a high pivot and idler, and the year before that a new Scalpel with the flex stays in the chain stay like the original rather than the seat stay like most brands. I feel like they get more traction in Britain and Europe. You see them a lot in race coverage from GMBN.

Habit is their recreational trail full suspension bike. Looking at the models, I like the Waves version. It's a slight upcharge from the next model down, for some meaningful upgrades - especially a Yari fork that has about the same performance as the 35 Gold, but can take all manner of upgrades compared to the Gold being a dead end.

Cannondale went bankrupt in the late 90s trying to get into the dirt bike market. They were scooped up by Pacific, a conglomerate that owns a lot of other familiar brands, both at the bike store in department store level, including GT, mongoose, and Schwinn. Last year Pacific was sold to Pon, who also own Santa Cruz and Cervelo. You start to see how despite there being a lot of brands, there are not really a lot of companies. You can buy a GT or a Cannondale or a Santa Cruz at about the same spec level and you’re still giving money to the same set of people.

I guess it depends what radar screen you're looking at. Cannondale is still very much alive in the pro racing world - road and MTB.

All companies have different levels of bikes with different levels of frames and components. Stay away from the lower level of Diamondback bikes as they cut costs by using lower level components and they may or may not be easily upgradable. Diamondback also sells higher quality bikes with higher level components that are worth considering. With any bike you're considering, do your research by looking at the specifics of the bike and also reading reviews from people who have ridden them.