Most part 121 airliners have fairly similar thrust and wing loadings, so in terms of throttle responsiveness they are largely similar. Stability characteristics are similar, as are control force inputs.
Cockpit equipment/layout, and automation levels differ greatly, however, from round dial 737-200s to the newer Airbus products such as the A320/330/340.
In terms of equipment or layout, "glass" cockpits put more information in a closer area, which makes the instrument scan easier or more rapid. Color screens make distinguishing b/t sky/ground, and bank angles easier. Digital readouts give specific info quickly, but are very poor in terms of conveying trends, hence the tape display...
In terms of cockpit automation, there probably aren't any easier a/c to fly than the newer Airbus equipment such as the A320. In normal operations when handflying the a/c, it will "Auto trim" itself in a climbing turn for example, as soon as the stick is released (obviously there's a litany of parameters at issue here, and flight control law/code) but in general they are very easy a/c to fly...they even tell the pilot when to "Retard" the throttles at landing.
An FMS equipped a/c is considerably easier to fly than a 727, 737-200 or DC9 for ex that doesn't have an FMS, simply b/c the autopilot knows the entire flight plan on an FMS equipped a/c, and requires no other input.