Metroid
Mario
Mario Kart

Grandia (1,2,3,xtreme)
Final Fantasy (1-X, x-2, XII, IV, V and VI again on DS, tactics, tactics advance, dirge of cerberus, crisis core)
Suikoden (1,2,3,4,5, tactics)
Zelda (twilight, windwaker, phantom hourglass, a link to the past, minish cap, four swords adventure)
star ocean (1, 2, 3,4)
devil may cry(1,2,3,4)
MGS(1,2,3,4, 1 remake (GC), metal gear acid 1,2)
Tales( legendia, symphonia, abyss, radiant world, phantasia, vesperia,)
Fallout (1,2,3, tactics, brotherhood)
Elder scrolls (oblivion, morrowind (all expansions), red guard, daggerfall, arena)
Dragon quest(7,8,4, masked queen)
wild arms (1,3,4,5)

Thats all I can think of right now

EDIT: top 5 would be Final fantasy, tales, suikoden, zelda, MGS

Do games i got twice for more then one system count?

Ok, lets see...

Command & Conquer: 10
Tiberian Dawn (PS)
Tiberian Dawn (PC)
Tiberian Dawn The Covert Operation (PC)
Red Alert (PC)
RA Counterstrike (PC)
Red Alert (PS)
Red Alert 2 (PC)
Tiberian Sun (PC)
Generals (PC)
Zero Hour (PC)

Sonic: 10
Sonic 1 (MS)
Sonic 1 (MD)
Sonic 2 (MD)
Sonic and Knuckles (MD)
Sonic R (PC)
Sonic Adventure Battle 2 (Gamecube)
Sonic Advance (GBA)
Sonic and the secret Rings (Wii)
Sonic Rush Adventure (DS)
Sonic Spinball (MD)

Fifa: 16
Fifa Soccer (MD)
97 (SNES?)
98 (N64)
98 (PS)
98 RTWC (PC)
2000 (PC)
2002 WC (PS)
2002 WC (Gamecube)
2003 (PC)
06 (PC)
06 WC (Xbox 360)
07 (PC)
08 (DS)
08 (PS3)
08 (Wii)
09 (Xbox 360)

Mario Main Series: 7
Mario Bros 1 (NES)
Mario Bros 2 (GBA)
Mario Bros 3 (SNES [All Stars])
Mario World (SNES)
Mario 64 (N64)
Mario 64 DS (DS)
Mario Galaxy (Wii)

Mario Kart: 5
Super Mario Kart (SNES)
Mario Kart 64 (N64)
Mario Kart Super Circuit (GBA)
Mario Kart DS (DS)
Mario Kart Wii (Wii)

Pokemon: 6
Blue (GB)
Red (GB)
Yellow (North American Version) (GB)
Yellow (PAL) (GB)
Stadium (N64)
Snap (N64)

Ratchet & Clank and Pokemon;

Ratchet & Clank
Ratchet & Clank: Going Commando
Ratchet & Clank: Up Your Arsenal
Ratchet: Deadlocked
Ratchet & Clank: Size Matters
Ratchet & Clank Future: Tools of Destruction
Ratchet & Clank Future: Quest for Booty

Blue/Red/Yellow
Silver/Gold/Crystal
Ruby/Sapphire

I plan on buying R&CF: ACIT when it comes out, and Emerald, Fire Red/Leaf Green, G/S remakes, and possibly D/P/P

Final Fantasy hands down, 11 games (1, 2, 4, 7, 8, 9, X, X-2, XII, Dirge of Cerberus, Crisis Core)

Then Mario (Mario Paint, Super Mario All-Star, Super Mario World 1 and 2) (Soon to be tied with MGS once I get 4)

Forgot to mention Tomb Raider: 1, 2, 3, 4, Angel of darkness, Legend, Anniversary and Underworld

FF - I have VII, VIII, IX, X, X-2, XII
Shin Megami Tensei - P3, P4, Nocturne

1.Mario (Platformers)
(All-Stars, Land, Advance 1, 2, 3, 4, SM64, SM64DS, Sunshine, Galaxy, Deluxe, SMB:LL (VC), SM64 (VC))

2.Pocket Monsters (Main)
(Red, Blue, Yellow, Silver, Crystal, Ruby, Leafgreen, Diamond, Pearl)

3.Legend of Zelda
(Zelda II (VC), Ocarina (VC), WW, TP, LttP, LttP/4S, Crossbow, PH, MC)

4.Art Style
(ORBIENT, CUBELLO, DECODE, AQUARIO, PiCOPiCT, nalaku, HACOLIFE)

5.Wario (Platformers)
(Land 2, 3, 4, World, MoD, Shake It)

(>'.')>

Wait,I have bought tons of Mario and Zelda games.

As much as I'm sure you'd like all five of your choices to be RPGs, you should really check your collection again. Sonic 3D Blast(Sat), Sonic 2(Game Gear), Sonic(Game Gear), Sonic Chaos(Game Gear), Sonic(Genesis), Sonic 2(Genesis), Sonic and Knuckles(Genesis) and Sonic Adventure(Dreamcast). On top of that, you have two spinoff titles(Sonic Spinball and Sonic Shuffle). That's definitely your number one.