This more mostly has to do with the later issues, since you can get a remastered version of Modern Warfare, with Infinite Warfare. While the original MW changed the multiplayer landscape, Modern Warfare 2 and Modern Warfare 3 refined the elements that made Call of Duty a household name. Modern Warfare 2's online play is often considered the pinnacle of the series. Everything from its perks to its kill streak abilities has been refined to a tee. Its story may have been hard to follow, but its campaign was filled with dozens of over-the-top sequences and tight gunplay.
MW3, Meanwhile, still has its charm. With its equally enjoyable campaign that does a decent job of wrapping up the trilogy and its expert multiplayer that's just as enjoyable as past games, MW3 shouldn't be missed out and worth a second look.