As far as Captain Britain is concerned, the Mad Jim Jaspers Warp is by far the best arc of any comic i've read.

For the Thunderbolts, you've just got a winner every time.

For the Guardians, i'd have to pick the recent rise of Adam Magus.

For Green Lantern, i think the Sinestro Corps War was darn incredible

For Thor, i'd pick just about any arc. almost always a winner.

the walking dead
age of apocalypse
batman: knightfall
days of future past
sinestro corps war



kingdom come was good for the time but maybe ive read it too many times and its lost its feel to me.

In no particular order:

90's Namor pre Jim Lee
Alpha Flight
Justice League International
X-Men First Class
Annihilation