When Mass Effect 2 came out early last year, there was a general outcry to the effect of "this isn't an RPG, it doesn't have complex inventory management!" Basically, fans of the role-playing genre have come to expect a certain amount of loot-collecting in games, and the lack of it in ME2 distressed them. Mass Effect 1 had four categories of guns and dozens if not hundreds of individual weapons to choose from, and that's not even starting on the armor, the biotic amps, omni-tools, or upgrades. ME2, on the other hand, had 13 guns (from 5 categories, not counting heavy weapons) on release, and perhaps another half dozen included in various downloadable content. Given this, it's easy to see why people were upset. ME1 had so much more to choose from.
Except not really. In ME1, all sniper rifles were basically the same, except that you found better ones later in the game. Not particularly different sniper rifles, mind you, just better. Often in every way. Sure, there were always minute differences between individual models, but mainly you were just looking for the highest level gun. And then sometime later you found an even higher level gun and used that. Can you see all the choices you're making?
Contrast ME2, in which you no longer loot random weapons after every battle. When you do find a weapon, it's a rare and important event, and the new weapon in generally very different from the old one. Take the sniper rifles, for example. There are four of them, counting downloadable weapons. The first three are about equal in utility, but their uses differ, from tradition one-shot kills to long-range sustained fire. Each gun is a choice, and which is better seems more a matter of play style and personal preference. The fourth sniper rifle is a clear upgrade, easily the most powerful of the four, but it's a unique weapon chosen from an array of potential advantages, and so has importance that a randomly looted gun never could.
What's the difference? Well, in ME1, you use whatever gun is best. In ME2, you use whichever gun you like, and if you invest in the true upgrade, that's a choice you make for yourself. In other words, ME1's guns are random and disposable, whereas ME2's guns are unique and interesting. You're not pulling out a random sniper rifle, you're pulling out the gun that you enjoy using.
So why is this a case against inventory systems? Technically, it isn't. It's a case against the constant quest for better equipment that drives almost all RPGs today. The inventory system, however, is pretty much the heart of that quest. You have an inventory filled with stuff and a bunch of equipment slots to fill with that stuff. Occasionally you find better stuff. At the end of the "Quest for the Sacred Sword" (or whatever) this is ok. You earned your better item with sweat and toil. After killing some random bad guy, or buying it from a merchant, or any other staples of the genre, it's just silly. Any emotional attachment to your equipment is replaced with stat-grubbing power-lust, and even if you do find a weapon you really like, eventually you'll have to upgrade because the game assumes you'll upgrade and if you fall behind it'll become impossible to win. This is especially glaring when you find yourself selling your grandfather's sword because it's just a tier 1 weapon and you're up to tier 4 and it's just cluttering up your inventory now.
This is not to say that all inventory systems are bad. In some games, particularly the post-apocalyptic Fallout series, it makes sense to spend most of the game scrounging for better loot. In those games society is dead, and trying to make do with limited resources and substandard equipment is pretty much the theme of the setting. Even so, it's sad when a favorite weapon gets replaced by one that's statistically superior, as inevitably happens in almost any modern RPG. In the case of Fallout and similar games, I would propose that the weapons be placed on a more even playing field, so that player could pick the ones they like, not necessarily the ones that do the most damage, but that items like food, water, bandages, and traps be made a more central part of the game. In this way, players could still experience the desperation of the wasteland without ever having to abandon their favorite gun just because it doesn't do enough damage anymore.