A few options.

The south street bridge (which connects University City with Center City). You can walk across it (though there's plenty of traffic) and you get a nice view. You'll get more of the view than you would from the Skuyllkill River trail, though that's lovely as well.

You can head over to Penn's landing - depending on where you are, you can walk along the marina and get some views of the city (with some nice ships in the foreground). A cruise down the Delaware River will also give you some city views.

You can also get a view from going up some of the buildings: Liberty Center/Liberty Place has an observation deck now. It also has a restaurant/lounge called R2L which has views of the city. Not so much the skyline (you're facing West) but you do get some of it, and food is decent and decently priced. Skygarten is also lovely - it's a rooftop beer garden, though the beer garden part is enclosed. You can go outside to get some great city views, though. I believe they also do tours of City Hall that let you get views of the city.