ICONS is a simple, unassuming game by veteran designer Steve Kenson (Mutants & Masterminds). The stated goal was for ICONS to be a pick up games, thoght it is not limited to that. It's a mix of the old TSR Marvel Super Heroes and Fate, bring together the best of older and newer styles in game design. The orginal ICONS leans more towards MSH, the current ICONS Assembled towards Fate. The origins of ICONS go back some 20 years when Kensons put his MSH to Fudge conversion notes on the web under the name the Superlative System (https://stevekenson.com/2005/07/01/superlative-system/ ). It's a easy fit as both systems were based on a English language adjective scale.
What I really liked about ICONS is the low fuss and the high levels of player engagement that emerged in play time and time again. I think the player engagement was due both with the player facing system (the original version of ICONS the GM doesn't roll dice) which keeps the spotlight on the players all the time and the way that Determination (Fate Points) always gave the players a creative options. The new version of ICONS has relagate player facing mechanics to an optional rule and rules around Determination are bit more complicated and Fate-like.
ICONS was also a very well supported system out of the gate with lots of good quality and cheap adventures and villain collections. Even if you don't run them as written it provides a lot of inspiration and adventure fodder.
An important thing to note is that ICONS uses random character generation by default. It's only really semi-random as there are many options to customise and swap abilites around, but this is still a deal breaker for many. ICONS does have a point buy system too, but it is not robust and it won't prevent players creating monstrously overpowered characters if that is their inclination. Also the art and many of the canonical villains are very cartoony. I kind of like that but a lot of people don't.