I'm in the market for a $500 hybrid bike and there seems to be many offerings from Trek, Giant, Fuji, etc.

In your opinion, what level of components are mandatory so that I get the best performance and durability for the money?

They seem to all use Shimano components, but which are the bare minimum for quality?

Typically, in bikes for $500 and less, about all I would suggest is that named components are typically better than numbered components. So, even though Acera and Alivio are at the bottom of the named groups, they are a step above those identified only by number. (although the named groups also have numbers. )

However, if you buy a hybrid in the $500 range from a bike shop, you will get reliable components. I bought my Giant Sedona DX 10 years ago for $350, and have rode for over 4,000 miles, and weighed anywhere from 300 to 365 during those years, and never had a problem with any components. I broke 1 spoke, and replaced tires a few times, but otherwise it was reliable. I believe it has a non-named (number only) front derailleur, and an Alivio rear derailleur...

I just upgraded to a used 2011 Trek 7.3 FX and it has a Deore rear derailleur, and I honestly don't really notice a difference component-wise, but the bike's geometry fits my riding style better.

Your bigger choices should really be made depending on how you expect to ride it. i.e. road only? some trails? mostly trails? commuting? Hybrids come in a mix of configurations from comfort bikes to flat bar road bikes...

If you can find an older bike, in the same model - you will get more for less dollars. Ask your dealer if he has any leftovers in your size.

It might be a little too late, but its very typical early in the year that bike stores will put out last years models at sometimes serious discounts....and usually the only difference between the old and the new is color

Regardless, once you have identified the overall series/style of bike, I encourage you to buy the highest tier you can. "Component envy" is human and almost inevitable. If you can afford an extra $100 but dont, you will probably wish you did.

I have an entry level Trek 7.1FX that has Tourney and Acera components and they work perfect. The only reason I see for the better ones are bragging rights.

Yes good point. Said another way, regardless of price Shimano derailleurs are well designed with specific models available for different riding situations. They are all durable and will all do the job of positioning the chain and taking up chain slack.

A couple of examples. My Giant FCR 3 uses Altus derailleurs and they continue to perform as the shifter directs them. My granddaughter is using a 2001 Giant 16" mountain bike with a Tourney 7 speed. The bike has helped three other kids learn to ride and still shifts perfectly.

However, my advice for the original poster is to shop for bikes from the big name bike companies. If you find a bike at the right price for you that fits the components used in similarly priced bikes from other companies will be of identical or comparable quality.

If $500 is the money on the table what it comes with is fine ... wear stuff out and buy pricier components, then, if you wish .