It's failing because other Portable Systems fanboys hate it and keep saying shit everywhere about it (no games, expensive, no pokemon, no mario, ...) even if they never played it! Also because most of SONY fans are "all I care is about playing games with amazing graphics on ma huge TV"...
Yes SLY Cooper is amazing... So sad Thieves in Time sold so bad... But hopefully it will have a new game tied to the movie in 2016
I also love playing PS1 classics on it, I did beat Tomba! (never ended on the PS1), Gex, Crash Team Racing, and just purchased Tekken 2 (man how could tekken be so good back on the day? Tekken 6 was so meh) and Wild Arms (still need time to start it!)
And there are so many AMAZING Vita games you need to try! Tearaway, Gravity Rush, Soul Sacrifice, Uncharted Golden Abyss, Persona 4 Golden, PlayStation All-Stars Battle Royale (yes trying it won't hurt you! I had a lot of fun with it and you can get to know many characters from games you missed for hating SONY!), Muramasa Rebirth, Sound Shapes, Dokuro, Destiny Of Spirits (free to play and addictive!), PS2 HD Collections like SLY COOPER (you said you loved it, now go check its roots), Ratchet & Clank (my fav PS2 Classic), Jak & Daxter and GOW...
That's not all, there are many AMAZING games coming out for Vita this year, like Freedom Wars, Tales of Hearts R, Oreshika Tainted Bloodlines and Sword Art Online: Hollow Fragment
Vita love forever <3 #ThisIsForTheVitaPlayers