I'm with fred2 on this for the most part. There was innovation in the early Silver Age, but whereas the Golden Age had been a gold rush of publishers throwing any superhero they could at the wall to see if it would stick, the DC Silver Age ultimately felt like a more canned product sold by a publisher who was a little too sure he knew what you wanted and was going to sell it to you without varying too much from the basic mould.

It's exactly why I like the Bronze Age and, to some extent, the Copper. You've got publishers fretting all over again about how to appeal to the older, more mature readership that was now making its voice and demand heard, and a lot of bold experimentation ensued.

Though I'd never considered it before, there's a lot of commonality between the DC Silver Age and Marvel in the 1990s: both sold products that felt meaningless and rolled off of an assembly line belt because they felt they had their customers pegged. Editors also, I think, wielded a lot more control over what creators could and could not do as a result. When a company thinks it knows what sells, it doesn't want to see anything in print that doesn't completely match that.

Also contributing to DC's non-innovative status from the mid 50s thru the mid-60s was the fact they were a closed shop. Essentially they were not hiring anyone new. It was the same group of editors, writers and artists for over 10 years. Granted many of them were quite talented but essentially it begins to get stale. Neil Adams and E. Nelson Bridwell or some of the select few that broke in. It wasn't until the late 60s with Marvel now recognized as seriously gaining in sales and a number of DC veterans getting fired for trying to start a union with health benefits that new blood came aboard. Most importantly it was folks like Dick Giordano and his Charlton pals (like Diko, Skeats, Aparo et al), Wally Wood, Marv Wolfman , Len Wein and Denny O'Neill who brought some newer concepts like Hawk & Dove, Secret Six, Brother Power the Geek and more

I agree with Repitsaurus that the DC heroes are the least interesting-- at least the Weisinger and Schwartz lines. They're fun to read, but don't have many surprises. I love the late silver and early bronze for the variety of new concepts, though most were short-lived: Secret Six, Bat Lash, Creeper, The Shadow, Swamp Thing, even Kirby's work. DC tried this to a certain extent in the 80 s as well: Nathaniel Dusk, Spanner s Galaxy, etc. But both periods they were trying to push against a market. Momentum for superheroes.

I gotta say, though, that I really have a hard time thinking of any Silver Age Marvels that don't involve Kirby or Ditko that I enjoy. Maybe Iron Man around the time Heck was drawing it. But they all feel like second- stringers.

A variety of other minor characters survived in back-up status-- which is the way both Aquaman and Green Arrow lasted-- though the only other headliners I can think of offhand are Tomahawk and Blackhawk (who was purchased from Quality by DC in 1956). By the time DC got finished with them, both were encountering so many monsters and costumed characters that one could easily term them and their coteries "quasi-superheroes."

I'm not sure what you're using as your criteria for "being derivative." The Golden Age is full of characters derived from franchises published in other media. The original Sandman is heavily indebted to radio's Green Hornet. Batman took elements from the Shadow and various bat-garbed characters. Hawkman borrows from Flash Gordon and John Carter.

It's valid to point out characters who are directly derivative from a template, like Batwoman from Batman. But a crimefighting partner like Mera isn't specifically derivative of Aquaman, so long as she isn't sporting some variation on his name or costume. She isn't even really derivative of Aquaman's earlier buddy Quisp, though the editors of the title certainly recycled his hard-water powers into Mera. But Quisp as a character was just one of many routine imp-characters, and Mera was a much more interesting character, even apart from her intrinsic hottitude.

I'm not even sure re-using a name is all that derivative when there's so little else in common. The Silver Age Red Tornado derives no more from the Golden Age version than Hawkman does from the "Hawkmen" of Flash Gordon.

Artists in all media constantly use and re-use tropes that have gone before, but all of these re-usages are not automatically derivative in the creative sense. 

There are some ways in which the Silver Age outstrips the Golden Age. The second Flash's villains, simple as they are, are far better developed than the foes faced by Jay Garrick.