the list can be big ! i have stopped listening to euro trance the last years but as far as i can remember...
Airscape - L'Esperanza (Armin van Buuren remix)
agree with Rotwang: Delirium & Sarah McLachlan - Silence Tiesto remix, even if i always thought this was overrated a bit, it's still good trance
Ferry Corsten - Sweet sorrow (Thrillseekers remix) - way better IMO
Paul Oakenfold - Southern sun (Tiesto remix)
Motorcycle - As the rush comes (Armin van Buuren remix) - to discuss of course some people will prefer Gabriel and Dresden remix
Mantra - Skies of gold (Hemstock and jennings remix)
Bobina - Invisible touch (Ferry Corsten remix) - Original is good really, remix is excellent, big credit to original of course
Oceanlab - Sky falls down (Armin van Buuren remix) - Remix way better
Moogwai - Viola (Armin van Buuren remix)
Shane - C'est musique (Armin van Buuren remix) - Wow just love this one, of course original is good, really unknown though, the remix is a classic
Madelyne - Beautiful child (Hiver & Hammer remix) - Original is quite weak, remix is massive!
I won't put Aria - Dido (Armin van Buuren remix) in the list cause original is not really trance, more on the chill side, remix is epic though!!
So yeah a lot of AvB remixes, i was into his trance style back then