The vanilla and chocolate gu gels are a thicker consistency - more like frosting (chocolate is super thick!). The banana/strawberry banana and plain ones seem to have the thinnest consistency. Some of the other flavors fall somewhere inbetween.

I use hammer, a mixture of banana and raspberry, but sometimes when I'm running it seems really strong flavored. They taste the most like fruit and the least like made-up-food (Gu is a good standby). Consistency is fairly thin, but it is sticky on your fingers. Power Bar gels grossed me out. Clif's gels taste like brown rice syrup and fruit, which is exactly what they are... it's more of a woody taste (hard to describe) than the others.

I use a flask during training, but often use single-serve packets during races (that way if I drop something, I'm not screwed - AND I get multiple flavors). I can't handle caffeine (increases GI problems and limits my effort, ironically), though I like the flavor of GU Roctane's blueberry pomegranate (they have that flavor in Chomps which I use when I ride/hike). For anything over 90 minutes, I would definitely use the gel, at least every 45.

Alternatives... bloks/chomps/moons/sharkies (good, but you have to chew - moons and sharkies are smaller, bloks the biggest), sports beans (again with the chewing), sports drink (harder to carry, but maybe use what they have at aid stations if you can stomach it), or thin out the gels and put them in a flask. If you really only need 2 servings, add water and make it thinner. As you get comfortable with it, make it thicker and thicker until you can handle it straight.

When I'm riding on the bike trainer, I like to eat straight fruit. Bananas, grapes, whatever I have. I wish that was easier to do for long distances and more portable.