Here's my personal top ten, in no particular order:
1. Resident Evil (and the sequels)- PSX This really invented a genre as far as I'm concerned. And to this day, it's one of the only games I've ever played that has startled me so much I nearly dropped my controller!
How would I improve it? Well, I haven't got RE4 yet; according to the reviews it's among the greatest platform games ever made, so maybe they already did.
2. MechWarrior 2-PSX Mech' 2 was one of the most incredible games I ever played. One caveat- you must have the large dual analog joystick console to go with it. Probably not everyones cup of tea, but the only thing I'd have done different would just be a few more missions and infinite "instant action" battles.
3. Diablo- PSX While I suppose most people here prefer the computer version, I'll take the PSX version any day of the week and twice on Sunday. I'm in the minority I realize, but I like the controller better than the keyboard. Plus, the infamous "belt pack cheat" only works on the PSX version. I've logged thousands of hours on this game and have beat it probably 100 times. Very few games have kept me playing for a decade. To improve it? Add-on disks with more dungeons.
4. HALO- Xbox One of the most incredible games I've ever seen. Really the only FPS I've ever been able to get into real deeply. It actually has more of a plot than you'd expect and the level design is really brilliant. The absolute Gold Standard for FPS's. The only way I could have improved it would be a little more Covenent and a bit less Flood.
5. Knights of the Old Republic- Xbox Hands down my favorite RPG ever. Pretty good graphics, good game engine and a better story line than
any of the six Star Wars films. The only things I'd change would be to tweak the way commands are layered. I'd already have an Xbox 360 if there was a
KotOR III for it.6. Ace Combat 2- PSX Again, only with the large dual flightstick as per Mech' above. This game had great graphics for the time, wonderful control that mimicked a real plane (pitch, yaw & roll- not just the "arcade joystick" controls). There are a lot of missions and all are fun and well designed. If I was to pick nits, I guess I'd have included a few more planes.
7. SoulCalibre- Dreamcast I'm not a very big fan of fighters, but this one was superb. Great controls, cool characters and graphics ahead of their time. Even thought SC2 for the 'Box and SC3 for the PS2 look a tad better, I keep my DC around just for this game. If I had to "improve" it, just a few more backgrounds or something.
8. Madden '92- Sega Genesis Even though the modern games blow it away for graphics, the AI and realism of '92-'93 are head and shoulders above the current crop with their 'money-plays'. I'll take the old ones for accuracy & playability. Improving it would involve grafting real AI onto the flashy looking new games.
9. BattleZone - Arcade If this post isnt' specifically asking for home videogames, I have to list this one right up there. Okay, it doesn't hold up as well compared to new games, but for the time it was remarkable. Sure, I was young, but my palms would sweat and my heart would race. The "periscope/viewer" did an excellent job of blotting out the outside world and focusing your attention on the action. Sadly, none of the console reissues really get the controls right, IMO. Improve it? Easy- not let the computer cheat!
10. TIE- Tomb Raider (PSX), Shingen the Ruler (NES) & Risk (PSX) Okay, this is maybe a cop-out way to get extras into my Top 10.
Tomb Raider was astonishing at the time: it really kicked off a new genre. It was amazing to explore in 3D environments like that, and no other game before offered what TR did. Yeah, it had some problems with the camera angles and too many block puzzles, but it was still quite a game.
Shingen the Ruler was a pretty deep and involved RTS, maybe the first RTS game. I must have played it over 1000 hours and united Japan dozens of times. In retrospect it was a bit simplistic, but hey- we're talkin' 3 bits here!
The huge appeals of Risk for the PSX or PC was that you didn't need a bunch of buddies and you didn't need to spend an hour setting up the board. Sure, the AI resorted to cheating much more than strategizing, but the addition of Super Weapons and Secret Mission Risk added depth to the game.
