My Top 5:

5.
SEGA Rally Revo (Rally Racing)
The NFSs for the PSP sucked balls,IMO..
and no other racing game looks as interesting as this.

4.
Ace Combat X Skies Of Deception (Flight Simulation)
Need no introduction,i think.
want a good solid arcade style flight/combat simulation video game,get Ace Combat.
accept no substitute.
ad hoc only,unfortunately

3.
Metal Gear AC!D 1/2 (Mixture Of Turn-Based Strategy With Card-Based Gameplay)
i prefer MGA's graphic style,but AC!D 2's gameplay is a little bit better.
toss up between the two.
only Ad hoc

2.
SOCOM: Tactical Strike (Action-Simulation)
Take SOCOM,and drop it into a tactical scenario,instant gaming heaven.
carry out infiltration and executions with great gameplay mechanics.
confusing control scheme at first,but becomes second nature as the game wears on.
Ad Hoc and Infrastructure supported

1.
Metal Gear Solid Portable Ops/MGS PO + (Stealth Action)
since MPO+ is an extension,i consider it one and the same.
an immersive story,great assortment of weapons and gadgets,amusing characters,and a phenomenal online component.

notable mentions:
Syphon Filter Dark Mirror (Stealth Action)
Syphon Filter Logan's Shadow (Stealth Action)
M.A.C.H. (Air Combat Racing)

main mpo+ la

Metal Gear Solid Portable Ops+