There's a little crossover between the weapons of Mass Effect 2 and the weapons of Mass Effect 3, but the first game in particular is just completely different.
Part of what makes it complicated is that how guns work varies between each of the three games in the series. However, picking what guns you want to use isn't as easy as you'd think. Given that the series is largely about blasting your way through space bad guys, finding the best weapons to fight Shepard's war in the Mass Effect trilogy is pretty vitally important.
