Would recommend a Boss DS-1 > Delay/Reverb pedal for a start. If you find the sustain/overtones are lacking, try a nice overdrive (Boss OD-3/SD-1/Digitech Bad Monkey/Ibanez TubeScreamer) before the DS-1 and back off the distortion a bit. That would make it more sustained and less fuzzy, like November Rain.
If you want a bit more upscale stuff, try out MI Audio's Crunch Box. It is a Marshal in a box sort of pedal. I have the Tube Zone and its lead tone is amazing (very Mesa-ish, Petrucci style).
Other popular Marshall-ish options are Fultone Full Drive, Keeley Modded DS-1 and Barber Direct Drive. But you would have to get these from the US as it would be tough to find these here.
-- My current rig
Guitar: '98 MIJ Ibanez RG520 QS w EMG 81/60
Amp: Laney LC15R Tube, Fernandes 20W SS
Pedals: MI Audio Tube Zone Overdrive, Boss OD3, CS3, MT2, HM2, DS2, CE5, DD7, TU3, Beta Aivin DD2 Delay, Dunlop Crybaby 95Q, Stranger Vol Pedal, BBE SupaCharger
Others: Yamaha RBX 374 Bass, Yamaha MM-6 Synth, M-Audio Fast Track, Shure SM-57, Heet Sound E-Bow Plus
Wanted(pm if selling): EB VPJr/Boss FV500L,Ibanez w Original/Lo-Pro Edge