Mass Effect is, and always has been, a cover based shooter which means that there are bound to be similarities to other cover based shooters. Beyond that, it's not actually all that similar to Gears of War. Mass Effect 2 was probably the closest in gameplay style.
There's plenty of variety and options in play style that pertains to combat. Especially classes like Vanguard have some unique gameplay styles.
On a side note after a few hours of MGSV the gunplay is serviceable but it's nothing impressive. It's nice that they offer the option to have a more "guns blazing" style, but it feels like most of their resources went into the stealth system.
Which actually about sums up how I feel about Splinter Cell combat, too.
Right, ME3 and Gears of War, from what little I've played of GoW, are pretty similar in terms of encounter design, a focus on run and gun shooting and taking on swarms of enemies. But with MEs build diversity and biotic/tech powers, the comparison really stops there.
While level design centered around stealth and slow tactical thinking wouldn't be necessarily be a bad thing, I don't see certain things we currently have working as well or in the same way in such a space. Like, I still want be able to equip a shotgun and blast through a bunch of enemies with Biotic Charge or Tech Shield. And I want to face down big alien brutes that charge and force me out of cover.