Denver has a lot of really great burger joints - from Bud's hole-in-the-wall to Crave's extensive and varied menu. So it's tough for a burger place to get great reviews from me here in Denver. With that caveat, Diego Zhang's is good, but not great. I'd go back, but only if I was in the neighborhood (taking in a movie perhaps).
Their menu of all sliders is pretty good, but a bit deceptive. They have beef, buffalo, chicken, pork, salmon, shrimp, and vegetarian sliders - which is a wide variety to start from. But then they don't get too inventive with them - and some are the same, just different meats. Watch for the Burger of the Month as an addition to the menu - when I was there, it was definitely the most inventive option.
The sliders are good sized - as big as a small burger at some restaurants. You're getting your moneys worth. Two is probably enough for most and one will satisfy a moderate appetite. The down side of the larger sized slider is that you don't get to try as many different items.
Bottom line: if you're in the neighborhood (The Streets at SouthGlenn), you'll get some fine sliders here. If you're on a quest for the best burger, try one of the other highly rated locations in Denver.