We are finally seeing a movement towards relegating inventories to secondary status in mass market games, a move that I believe is helpful to increasing the appeal of games - case in point, games such as Halo and Mercenaries which allow the player only two weapons, or Rogue Trooper, which allows its single weapon multiple roles. While any game rooted in the traditions of role-playing games is likely to maintain an inventory, these are gradually adapting to their new role as a mechanism of interest chiefly to the (increasingly large) minority audience of game-literate players.
I am not against inventories - they make sense for games in which planning an expedition is part of the play (many but not all role-playing games), for games using plenitude of objects or clues for puzzles (adventure games), for any game in which logistical play centred around trade is key (such as space trading games a la Elite, or various other kinds of role-playing games) and for any game wishing to create tension by providing strict limitations (survival horror games, for instance). But I do not believe that inventories are necessarily a good idea for an audience with low game literacy, such as the mass market audience in general.
I increasingly believe that the single largest barrier to wider audience is steepness of learning curve, and that the largest single factor in this is dimensionality of control, that is, the complexity of the interface.
There are two particular costs to inventories which hurt mass market appeal:
1. They add to learning curve. The player must learn a control to access the inventory, then (usually) learn a custom set of controls to operate the inventory.
2. They often add to dimensionality of control e.g. by adding +1 dimension for scrolling left or right through the inventory. This also produces very clumsy play from time to time, as players fumble through their inventory for the right weapon or tool!
3. They undermine engagement by forcing the player to switch between direct play and inventory management.
Remember, I'm not against inventories, I just think they are not helpful for mass market appeal. Superior solutions when dealing with a widespread audience include:
1. Context Sensitive Inventories
We already see considerable use of context sensitive use of items - such that the Action button will use the correct item in the correct context. The only example I can think of on the fly is the use of items in Project Zero/Fatal Frame, whereby each situation requiring an item automatically uses the correct item (if anyone remembers other games where the items are always used in a context-sensitive form, please jog my memory!)
This can become complicated at the design level, because it is necessary to ensure that the game contains no overloaded contexts. Still, better to give a complex probem to the game designers, who thrive on complexity, than to the players, who may not!
We could even see context sensitive weapon use, if we wanted to: enemy out of range, auto-select sniper rifle; enemy at far range, auto-select assault rifle; enemy at mid-range, auto-select SMG; enemy at close range, auto-select shotgun; friendly targets present, auto-select pistol; enemy too close for guns, auto-select melee. (This should be viewed solely as a preliminary suggestion for such a scheme, not an ideal case).
If there is potential for Hardcore players to be frustrated by not having direct control, an alternative control configuration giving manual control can also be provided.
2. One or Two-Slot Inventory
Remember the classic arcade games, where you had a simple choice of which weapon to take (as in Contra, or in Nemesis/Gradius with the choice between three way or laser)? These games didn't need inventory controls, because they only gave you 'one slot'.
More common these days, we see a two-slot weapon inventory as with Halo, Mercenaries and presumably others. (Other citations in this regard welcomed!) These systems are fantastically efficient! They require only one control, and its function is clear (switch weapon). A context sensitive option to switch weapons for others that are found gives the player a choice of kit. It is an excellent balance point, especially when backed up with additional static functions (such as a grenade button in Halo, or the knife in Resident Evil 4).
In a multiplayer co-op situation, the limited weapon allowance permits each player to develop their own role. (When everyone is multi-role, the most competent player does all the work, while everyone else is relegated to practically spectator status).
3. Toolkit Inventories
The idea here is the player does not acquire new equipment in the game, but tackles the play of the game with a fixed set of tools which are always available throughout the game (or throughout a particular episode).
We haven't seen this much in use, but this was an idea we were toying with for an atmospheric adventure game called 8, with Tale of Tales (the Endless Forest people - and note, the new version of this is out with a considerably more expressive interface). It is also reminiscent of the "Freedom Kit" used in the classic Monty on the Run (which was an early context sensitive toolkit), although a flaw in this case was that the player was very likely to pick the wrong escape kit and therefore be unable to complete the game - still, it was a tougher world for players in the 8-bit era!
This is an alternative to an inventory, but it doesn't solve the issues of inventory selection, per se. Perhaps it must be coupled with one of the two previous solutions to make it viable for a wider audience.
We will always have some games with inventories, but we are at last entering a time when player-operated inventory systems are being recognised as clumsy in respect of a wider game audience. Ironically, the 'new' inventory replacements have their roots in much older (8-bit) games, but delivered in shiny new games they seem refreshingly new. I have high hopes that in the near future we may see these ideas taken even further. Who knows what new replacements for the classic inventory we might see in the next decade?