Light gun games aren't anything new. The first game I remember was Duck Hunt on the NES, and the first arcade game I remember was Lethal Enforcers, though I imagine there are earlier examples. I don't recall too many console light games from generations past (as I wasn't a gamer for most of them, and they weren't prolific), and I don't recall any of them having much function other than pull the trigger.
Most of the innovation for light gun games seemed to happen in the arcade. I don't know whether early gun games had unlimited ammo, but I believe the first mechanic other than just shooting enemies was aiming and firing off-screen to reload. While I didn't mind House of the Dead, it was pretty hard (or I'm just a bad shot) and you had to be a good shot to get anywhere. Another notable early light gun game was Virtua Cop. I also remember a House of the Dead sequel, I think it was 3, that had 3 players, 2 of which had pistols, and one who had a shotgun.
But it was Time Crisis that really got me to sink money into a cabinet. In case you haven't played it, it has a foot pedal. If you don't have your foot on the pedal, you remain in cover and can not be shot. Putting your foot down has you come out from cover so you can fire on your enemies, but makes you vulnerable. This gave you something that many other light gun games didn't; control. The others demanded you be accurate at the exact right time, but Time Crisis let you hang back if you were coming under heavy fire, and this remained a staple for the series and spin-offs. In fact, since playing Time Crisis, I don't think I've ever played any other gun series in an arcade. The series had some other minor but notable innovations (at least, this is where I noticed them first) such as being able to hold multiple weapons and change them while playing, and while I haven't played Time Crisis 4, I have seen it played and it seems there are a few segments where you can aim at the edges of the screen to turn and face enemies coming at you from different directions.
As stated earlier, most home versions of these guns haven't had too many features, but the Wii Zapper gives plenty of options with a number of buttons and an analog stick available to use, as well as motion controls. I have played 3 games using the Wii Zapper; Links Crossbow Training, Ghost Squad, and Medal of Honour Heroes 2, leaving Resident Evil : Umbrella Chronicles as the notable game I haven't played.
Links Crossbow Training has a few different modes; standard on rails shooter/target ranges, 360 degree sections where you are stationary and turn by aiming at the edges of the screen, and free-roam sections where you move with the analog stick and aim at the edges of the screen to turn. Probably the best feature is holding Z to zoom in on the area you currently have your cursor for more precise aiming.
Ghost Squad is an on-rails light gun game throughout. It does let you unlock new guns and uniforms once you earn enough rank from extra playthroughs (I managed to unlock 2 guns which seemed worse than your standard one... shotguns are not hostage friendly), and play ninja and bikini party modes, which are new skins on the same gameplay, but fun enough to warrant replays.
MOH : H2 takes your standard WWII first person shooter and gives it Zapper controls, thus you can do almost anything that you would normally do in those games. It makes things interesting by offering decent motion controls; swinging the Zapper up to reload, punching it forward to melee, and tilting the Zapper to the side to lean out of cover. It does also have an Arcade mode, which plays more like a standard rail-shooter, moving you automatically through the same levels. It does still let you crouch at any time, which can keep you out of the line of fire if you happen to have a mid height obstacle between you and the enemy.
While rail shooters can be fun to play a number of times, console versions do need a bit extra to keep them going to warrant paying full price for them. Link was a nice pack-in that has replay value because of the scoring system, and MOH : H2 is really a first person shooter. Here are a few things I'd like to see in Zapper rail shooters to make them different or give them longevity (some of these might apply to the GunCon too).
Calibration - Apparently this was done in House of the Dead 2 & 3. I'd be happy spending 15 seconds aiming at some dots at the start of the game to be closer to actually aiming down the sights, which is perhaps the biggest criticism levelled against the Zapper.
Bullet Time - This might sound silly to some, but I think it would be kind of cool; earning bullet time similar to Stranglehold, and holding a button uses it up to slow down time so you can hit weak spots or fast enemies. Again like Stranglehold, it could even tie in to using the environment to kill enemies to earn more of this bonus (ie shooting a sign so it falls on enemies heads instead of blasting them directly in the face).
Only use B, C and Z buttons - This might just be my preference, but if I am using the Zapper, I don't want to have to use buttons that are on top of the remote. I know the games want to add more complex actions, but using the other buttons interrupts the flow of the action. Sticking to these buttons and motion controls would be preferable to me. Holding C or Z to bring up a radial menu for weapon changing or other actions seems workable.
Third person - It can still be on rails, but having a 3rd person view allowing some limited character movement would be nice. For example, a fixed view might have a row of crates that your character can hide behind, and pressing up on the analog stick raises you from cover, and you can move left and right as well to get better angles. You could also fire from cover with an obvious accuracy disadvantage. Enemies could also blow up your cover if you don't deal with them quickly enough, keeping the pace brisk. This point of view would also allow two players on screen at the same time while still allowing for the cover mechanics. Actually, that wouldn't be third person, but a fixed camera with your two characters in the foreground, but you get the idea. Think Gears of War but you have to stick to the same piece of cover.
Wiiware - The games don't all need to be modelled in 3D and have fancy physics for all the targets and such. A new Point Blank game seems like it would be a good fit for the service. Or even a new version of Duck Hunt. This combats one of the rail shooters shortfalls; value. They are usually most fun during the first few hours, and $10 for a couple of hours of rail shooting is fine by me.
Zoom - I liked this feature enough in Links Crossbow Training that I think it should almost become standard in single player settings. If designed properly, the benefits of greater accuracy should be offset by not seeing other enemies/targets while zoomed for the right mix of risk/reward.
Balance Board - I find it highly unlikely that a developer would want to take this risk, but what about a game that combined the Zapper and the Balance Board? I'm not even sure what I'm thinking as far as control goes, but it could be kind of neat. Maybe it detects your weight, and leans you in that direction. Or maybe each scene in the game lets you strafe left or right by leaning in the direction. I'd guess that the frantic pace of most rail shooters might make smooth moving while trying to aim with the Zapper a challenge to design for though.
Does anyone have any other thoughts on how to make rail shooters more appealing and valuable to the console gamer? Puzzle games mixed with other genres seem to be all the rage right now...